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Item type: Item , Investigation of The Plasma Reaction Behavior of a Coke Oven Gas with Trace Oxygen in a Coaxial DBD Reactor(Dordrecht : Springer Science + Business Media B.V., 2025) Nitsche, Tim; Lohmann, Heiko; Budt, MarcusThe presented study shows experimental results with literature comparison for understanding of the oxygen removal in coke oven gas (COG) with plasma. The reaction of oxygen with the main COG components H2, CH4, and CO are investigated as well as the occurrence of potential side reactions as the splitting of CO2 and CH4. Further potential side reactions in the COG mixture known from literature as hydrogenation reactions are discussed in contrast to the observations of the experiments.Item type: Item , Plasma-Assisted Non-Oxidative Coupling of Methane: Effects of Bead Size Distribution and Operating Pressure in a Co-axial DBD(Dordrecht : Springer Science + Business Media B.V., 2025) Larsen, T. S.; Andersen, J. A.; Christensen, J. M.; Fateev, A.; Østberg, M.; Morais, E.; Bogaerts, A.; Jensen, A. D.A co-axial packed-bed DBD reactor was used to conduct plasma-assisted non-oxidative coupling of methane (NOCM) utilizing glass beads as packing material at a fixed plasma power of 30 W. The influence on NOCM of five different bead size distributions (2000–5000 µm, 900–1100 µm, 425–600 µm, 212–300 µm, 150–212 µm) and operating pressure (1.2 bar, 1.7 bar) was investigated. The observed products consist of a mixture of saturated and unsaturated C2–C5 hydrocarbons. The conversion of methane decreased from 8.5 to 3.7% with decreasing bead size, while the selectivity towards unsaturated C2 compounds increased from 16 to 50% with decreasing bead size. These reactor performance variations are associated with the transitional plasma dynamics and degree of partial discharging, as determined by characterization of non-ideal charge–voltage plots for the five tested glass bead sizes.Item type: Item , Valorization of C2 + Hydrocarbons Via Plasma Processes(Dordrecht : Springer Science + Business Media B.V., 2025) Cameli, Fabio; Stefanidis, Georgios D.Hydrocarbon chains produced as byproduct of natural gas extraction and petrochemical processing can be valorised into syngas/H2 and oxygenated fuels in a modular fashion through electrified modular plasma reactors. A plethora of configurations is available for light hydrocarbons reforming, with cold plasma assemblies emerging as the favourite option for both gas-phase and biphasic gas/liquid set-ups. Accurate control of dehydrogenation or partial oxidation reactions is provided by the implementation of a catalyst or through microreactor technology. On the contrary, warm plasma reactors are more suitable for reforming of gasoline/diesel chains, promoting higher throughput of H2 per energy input. This reaction route does not necessarily require the deployment of a catalyst, hence making these systems more suitable for modular, decentralized processes. Online diagnostic techniques shed light on the reaction mechanism, where solid carbon deposits embody a low-value byproduct.Item type: Item , Is Plasma Activated Water Really Magical? A Reflection on the Phenomenon(Dordrecht : Springer Science + Business Media B.V., 2025) Scholtz, Vladimír; Jirešová, Jana; Lokajová, Eliška; Měřínská, Tereza; Thonová, Laura; Šerá, BoženaA reflection on the phenomenon of plasma-activated water (PAW), its brief history and properties. PAW arises from the accumulation of reactive plasma products (mainly H2O2, NO2−, NO3−, O3 and sometimes HNO, ONOOH) in water and has many interesting and beneficial properties on both living and non-living biological objects. It has attracted considerable attention in the last 15 years and raises the question whether it might not be simpler to prepare it artificially (APAW) directly by mixing chemical compounds. There are several papers which have compared the effects of PAW with APAW and conclude that there is probably no significant difference. In this paper, we conclude that the preparation of PAW is several times more expensive than that of APAW. However, we also note that there may be specific situations in which the production of PAW could be advantageous, such as its efficient role in storing energy in the form of nitrate ions, which can serve as a nutritional source for plants.Item type: Item , Investigation of Capacitively Coupled Radio-Frequency Argon Plasma: Integration of in Situ Optical Diagnostics with Data-Driven and Theoretical Modeling(Dordrecht : Springer Science + Business Media B.V., 2025) Atlas, Sharona; Har Lavan, Shani; Kaplan, Amir; Lehrer, Avi; Rozenberg, Illya; Zhao, Hao; Baraban, Joshua H.We utilized a combination of experimental alongside data-driven and theoretical modelling techniques to study non-thermal plasma properties and observables including optical emission spectral intensities, electron temperature, species concentrations, degree of ionization, and reaction rates. As a case study we measured the plasma properties of Argon gas in the low-pressure regime using optical emission spectroscopy (OES) while varying plasma input power and gas flow rate. We used data-driven and drift-diffusion modeling techniques to obtain complementary information, including electron temperature, reduced electric field, and species densities. The calculated density number of excited argon has a linear correlation to measured emission intensity, and we found that the dominant effect on Ar I intensity is the applied power with the gas flow (or pressure) the secondary factor (77% and 20%, respectively). The electron temperature increases with power but decreases with flow (or pressure). Combining the measured and modelling results help to understand the cold plasma dynamics and chemistry towards more complex plasma chemistry applications.Item type: Item , Reduction of MnO Using a Thermal Hydrogen Plasma(Dordrecht : Springer Science + Business Media B.V., 2025) Aarnæs, Trygve; Jensen, Roar; Fritzsch, Robert; Dalaker, HalvorHydrogen (H2) plays an important role in meeting the demand for carbon-free steels. When reduction is done with H2, harmless water is released as the off-gas, instead of CO2 generated by reduction with carbon. While steel can be produced using H2, many of its alloying elements cannot. As a result, fully carbon-free steel production necessitates a carbon-free production of its alloying elements. An important alloying element for steel, manganese (Mn), is subject to thermodynamic limitations that makes reduction with H2 infeasible. If instead a much more reactive hydrogen plasma is used these thermodynamic limitations would disappear. The current work shows an in-depth investigation into the reduction of manganese oxide (MnO) by a thermal hydrogen plasma under various conditions. By passing H2 through a plasma torch before it contacts an MnO-containing slag, formation of metallic Mn was achieved with a hydrogen-based reductant. Investigating the reduced samples with an electron probe micro analyser (EPMA) the amount of Mn formation in different conditions is mapped out. The reduction was found to be favoured when the torch was operated with a transferred arc mode, and for slags high in MnO, if the melting point was not too high. While the research into reduction of stable oxides with thermal hydrogen plasmas is still in an early stage and there are many unanswered questions, the work presented demonstrates the possibility of hydrogen-based manganese production.Item type: Item , Influence of Gaseous Oxygen Species on Liquid-Phase, Fixed Nitrogen Products in Aqueous Plasma-Based Electrochemical Processes(Dordrecht : Springer Science + Business Media B.V., 2025) Kamiyama, Brandon; Eslamisaray, Mohammad Ali; Gillmore, Emily; Sankaran, R. MohanElectrified, small-scale, remote approaches are needed as an alternative to conventional centralized methods for nitrogen fixation in order to reduce our reliance on fossil fuels and ensure global food security. Plasma-based electrolytic processes offer a promising solution by directly reacting molecular nitrogen and water under mild conditions. However, the complex non-equilibrium chemistry results in a diverse range of gas-phase and liquid-phase reactions, which impacts selectivity toward desired products. In this study, we investigate the influence of feed gas composition, specifically the presence of molecular oxygen at minute quantities, on the liquid-phase nitrogen products. Specifically, oxygen gas concentrations as low as 0.1% in the gas feed are found to substantially affect the selectivity towards ammonium ions. We additionally show that the total gas flow rate has an indiscriminate effect on both ammonium and nitrate/nitrite ion yields because of the presence of water vapor. By carefully controlling these process parameters, a production rate for ammonium ions exceeding 1 mg/h with a molar selectivity of ~ 14 is achieved. Our results highlight the importance of gas-phase chemistry in plasma-based electrolytic nitrogen fixation.Item type: Item , A SDBD Reactor for the Removal of Oxygen Traces in Hydrogen Operated above Atmospheric Pressure: Experiment and Simulation(Dordrecht : Springer Science + Business Media B.V., 2025) Oberste-Beulmann, Christian; Wirth, Philipp; Mohsenimehr, Soad; Oppotsch, Timothy; Keudell, Achim von; Awakowicz, Peter; Muhler, MartinNon-thermal plasma-based technologies have emerged as versatile tools for various industrial processes due to their ability to induce chemical reactions efficiently under ambient conditions. In particular, dielectric barrier discharges (DBDs) are of interest because of their robust and reliable design and scalability. This study investigates the role of pressure in tuning conversion, plasma parameters, and flow patterns in a plasma-assisted chemical reaction using a surface DBD (SDBD) reactor. The removal of O2 traces in H2 was used as a model reaction, where an unexpected increased conversion at elevated pressure was observed at high powers. This effect was studied using high-speed photography to analyze streamer dynamics and optical emission spectroscopy to determine plasma parameters. With increasing pressure, both the plasma area and the number of individual streamers decreased, and the electron density decreased as well. Fluid simulations were conducted to examine the impact of increased pressure on mass transport pointing to an enhanced contact time as the origin of the increased conversion at high dissipated powers. The findings highlight the importance of optimizing pressure and power conditions to maximize the efficiency of plasma-based chemical processes.Item type: Item , Nitrogen Oxidation on A Plasma-Exposed Surface(Dordrecht : Springer Science + Business Media B.V., 2025) Vervloedt, Steijn; von Keudell, AchimThe elementary processes during the fixation of nitrogen by plasma catalysis are studied in a low-pressure plasma experiment with N2 and O2 as source gases. The formation of surface groups on an iron oxide foil is monitored with infrared reflection absorption spectroscopy. Surface nitrates (NO3-) are formed when the substrate is exposed to a 1:1 N2:O2 plasma, as well as N2O(g), NO(g), NO2(g), and O3(g) in the gas phase. It is postulated that NO1,2(g) species created by the plasma, adsorb at the surface and create these nitrates. This constitutes an intermediate step for nitrogen oxidation by plasma catalysis.Item type: Item , Transient Spark Discharge and Ozone-Driven Nitrogen Fixation to Water(Dordrecht : Springer Science + Business Media B.V., 2025) Pareek, Pankaj; Selvaraj, Gokul; Hensel, Karol; Janda, MárioFixation of nitrogen and the generation of plasma-activated water are currently a significant focus within the low-temperature plasma research community. This study examines the enhancement of nitrogen fixation in water, by converting the weakly soluble nitrogen oxides (NO and NO₂) generated by transient spark (TS) to highly soluble dinitrogen pentoxide (N2O5) and nitric acid (HNO3) in the gas phase. This is achieved by mixing ozone (O3) with air that has been treated by a TS discharge. Without O3, only nitrite ions (NO2−) are detected in the water, formed primarily due to reaction between solvated NO and NO2. With addition of O3 (400 ppm), the composition of species in water significantly changes depending on the initial NO/O3 ratio. An excess of O3 enables formation of N2O5 and HNO3 in the gas and a high concentration of nitrate ions (NO3−) in the water. With an excess of NO, the dominant gas phase product is NO2 and a mixture of NO2− and NO3− is formed in the water by reaction between solvated NO2 molecules. Despite the additional energy required for O3 generation, the overall energy efficiency for the formation of NOx− (NO2− + NO3−) in the water increases fourfold, when enough N2O5 is formed. Further improvements are possible by optimizing the use of O3 and ensuring all N2O5 is captured from the gas phase.Item type: Item , Analysis of Mixed Composition Cold Plasmas by Optical Emission Diagnostics and Simulations(Dordrecht : Springer Science + Business Media B.V., 2025) Har Lavan, Shani; Atlas, Sharona; Kaplan, Amir; Lehrer, Avi; Rozenberg, Illya; Zhao, Hao; Baraban, Joshua H.The behavior of mixed composition cold non-equilibrium plasmas was investigated in a low-pressure capacitively coupled reactor using optical emission spectroscopy (OES). By fitting experimental data to simulations of the Second Positive System () of N2, rotational and vibrational temperatures were determined for various Ar/N2 mixtures as a function of plasma input power (40–100 W) and pressure (300–700 mTorr). Simulations of the plasma were performed for comparison. For pure N2, the observed trends revealed that both the rotational and vibrational temperatures increased with input power, (of increased from 369 to 396 K and from 5938 to 6542 K, at 40–100 W, 100 SCCM and 293 mTorr) but both temperatures showed minimal response to the applied changes in pressure. The rotational and vibrational temperatures for the mixed composition Ar/N2 plasmas were significantly higher compared to the pure N2 plasmas (e.g. of 1308 K and of 7279 K for 1.8% of N2 in Ar; at 50 W, 4 SCCM of N2, 220 SCCM of Ar for a total pressure of 587 mTorr). Moreover, the addition of Ar caused a larger separation between the rotational and vibrational temperatures compared to the pure N2 case. These phenomena illustrate the effects of Ar on the non-equilibrium energy distribution and more generally the influence that the gas mixture composition may have on the plasma reactivity.Item type: Item , Electrochemical Detection of NO and Ca2+ during Cold Atmospheric Plasma Treatment of Acute Wounds: Sensor Selectivity and Stability in the Plasma-Bio-System(Dordrecht : Springer Science + Business Media B.V., 2025) Thomas, Jonathan E.; Pattison, Kristina; Kumar, Suneel; Karkada, Gagana; Trosan, Duncan; Goodin, Aunic; Rainone, Jason; Rananavare, Dnyaneshwari; Miller, Vandana; Berthiaume, Francois; Stapelmann, KatharinaCold atmospheric plasmas (CAP) are a versatile tool in medical applications like wound healing. Its therapeutic benefits are partially attributed to the generation of biologically active reactive oxygen and nitrogen species (RONS). Characterization of RONS, however, typically only occurs after treatment. Here we report the first real-time in situ detection of CAP-generated nitric oxide (NO), and the simultaneous detection of cellular calcium ions (Ca²⁺) release using electrochemical sensors during CAP treatment of murine wounds. In vivo, NO rose rapidly within the first minute of CAP treatment but accumulated less overall than in PBS, reflecting reactions with wound-bed targets. In situ measurements revealed nearly double the concentrations of static endpoint assays, underscoring the importance of real-time detection. Ca²⁺ signals displayed transient, burst-like increases, likely due to CAP-induced membrane permeability and as response to oxidative stress. We also investigated the sensitivity, selectivity, and stability of the graphene oxide coated NO sensors and ion-selective Ca²⁺ sensors. Interference studies showed that the NO sensor also responds to H2O2 and NO2− yet remains most sensitive to NO. Raman microscopy revealed progressive degradation of the graphene oxide layer after only one hour of CAP exposure, drastically reducing sensor currents. Improvements in NO sensor design will enable more accurate measurements for feedback control for plasma-based wound therapies. Ca²⁺ sensors are more robust and retained full functionality after three hours and repeated use providing a reliable diagnostic for immediate biological response. The results establish real-time electrochemical sensing as a powerful approach to monitor CAP-tissue interactions.Item type: Item , Fluorine Substitution and CO2 Production in the Treatment of Perfluorooctanoic Acid in a Radial Plasma Discharge Reactor(Dordrecht : Springer Science + Business Media B.V., 2025) Tomei, Giulia; Saleem, Mubbshir; Scalvini, Filippo; Paradisi, Cristina; Marotta, EsterThe paper reports and discusses the results of a detailed investigation of transient products and mineralization extent achieved in treatments of perfluorooctanoic acid (PFOA) in a radial plasma discharge reactor. The efforts were warranted by the excellent performance of this reactor in terms of process efficiency and by the need to verify that the quality of the treated water was of matching value. Minor amounts of transient products were detected and quantified, as a function of plasma treatment time, by means of LC/MS and LC/MS/MS analyses. These products arise from sequential chain-shortening, an established route for plasma induced PFOA degradation, and defluorination via fluorine substitution by -H and -OH groups. We focussed on the latter less known type of products (“substitution products”), which are formed in small amounts, cumulatively accounting, at any treatment time, for less than 2% of the total carbon content initially present as PFOA. In our system, hydroxy-containing substitution products with 8–6 carbon atoms are remarkably less reactive than their perfluoro- and hydro-substituted homologues, an effect attributed to improved solubility into the aqueous phase and removal from the plasma/liquid reactive interface. Mineralization extent and carbon mass balance were also determined by performing experiments with PFOA at high initial concentration (1∙10− 4 M) to afford quantification of the CO2 released into the gas phase by means of GC-TCD analysis. Despite the low rate of PFOA decomposition entailed by these abnormally high concentrations, remarkable carbon mass balance of 75% and mineralization extent of 67% were achieved in 90 min.Item type: Item , Atomic Layer Etching in Patterning Materials: Anisotropy, Selectivity, Specificity and Sustainability(Dordrecht : Springer Science + Business Media B.V., 2025) Smith, Taylor G.; Chang, Jane P.Continued advances in semiconductor manufacturing depend on the 3D integration of complex materials, with nano-scaling precision patterning being a key limiting factor. This article discusses several important aspects of plasma-surface interactions to support atomic scale precision in patterning novel materials. This includes the effect of ions that control the etch anisotropy, the role of surface chemistry that dictates reaction specificity and etch selectivity, and the broader impact of the plasma applications on chemical processing sustainability. A systematic approach is discussed for developing an atomic layer etch process, which allows for independent control of surface modification and product volatilization at low temperatures. This approach starts with predicting a plausible etch product and thermodynamic screening of possible reaction mechanisms, choosing the appropriate half-cycle reactants, leveraging chemical reactivity, and counterbalancing etch and deposition as possible pathways of achieving greater selectivity. This can be followed by experimental verification of the etch rates, product formation, and etch selectivity. Finally, it discusses how these ALE processes can be leveraged to enhance the overall chemical processing sustainability.Item type: Item , Novel Jet Stability Evaluating Method for DC Plasma Torch(Dordrecht : Springer Science + Business Media B.V., 2025) Cao, Xiuquan; Chen, Weiming; Liang, Yunhao; Liu, Xing; Li, Bin; Tang, YufengThe jet stability of a DC plasma torch affects not only the service life of the torch but also processing consistency in industrial applications. To evaluate both instantaneous and longstanding jet stabilities of a plasma torch, a novel jet stability evaluation method has been developed in this study. The collected raw signals were first analyzed using the fast Fourier transform and filtered with identified characteristic frequencies. Based on the filtered signals, a 200 ms sliding window method was employed to evaluate the relative fluctuation of arc voltage in terms of both longstanding and instantaneous jet stabilities of the plasma torch. The results show that: (1) the proposed method can effectively evaluate both instantaneous and longstanding jet stability of a DC plasma torch; (2) the arc voltage and arc current signals contain a characteristic frequency, which is strongly influenced by the gas flow rate; (3) the laminar plasma torch operates stably at an arc current of 90 A, and its longstanding jet stability improves with increasing gas flow rate. The findings and proposed method provide informative guidance to those interested in the improvement of plasma jet stability and processing consistency.Item type: Item , Underwater Plasma-Driven Decomposition of Tetramethylammonium Hydroxide (TMAH) Under Different Applied Field Strengths(Weinheim : Wiley VCH, 2025) Lee, Ki‐Taik; Lim, Hana; Park, Sung Cheol; Bae, Jin‐Young; Kim, Sung‐MinTetramethylammonium hydroxide (TMAH), a toxic and persistent compound widely used in semiconductor manufacturing, was degraded using underwater plasma at applied fields ranging from 0.8 to 10 kV mm⁻1. Optical emission spectroscopy revealed OH(A–X), Hβ, and O I features, with Stark broadening of Hβ indicating electron densities between 5.0 × 1024 and 11.8 × 1024m⁻3, characteristic of high-field discharge. Spectral analysis showed a field-dependent shift from OH-dominated to O-dominated chemistry. Total organic carbon (TOC) removal followed pseudo-first-order kinetics, with rate constants increasing from 3.6 × 10⁻3 to 7.7 × 10⁻3 min⁻1 but plateauing above 4.8 kV mm⁻1. Ion chromatography detected NH4+ and NO3⁻ accumulation, suggesting that oxidative flux was partially diverted toward nitrogen conversion, thereby competing with carbon mineralization.Item type: Item , Comparison of the Coating Structure of Silicon-Based PECVD Coatings With Varying Organic Content(Weinheim : Wiley VCH, 2025) Franke, Jonas; Liedke, Maciej Oskar; Schäfer, Andreas; Butterling, Maik; Attallah, Ahmed Gamal; Hirschmann, Eric; Wagner, Andreas; Dahlmann, RainerThis study examines the structural transition between plasma-polymerized silicon-oxide (SiOx) and silicon-organic (SiOCH) coatings with varying organic content. Using comprehensive characterization techniques on 13 samples with systematically varied oxygen-to-hexamethyldisiloxane ratios and energy densities, we found that SiOx barrier coatings unexpectedly exhibited higher porosity than SiOCH coatings. This suggests chemical composition impacts barrier performance more than nanopore structure. The transition from SiOCH to SiOx involves molecular-level structural reorganization, likely due to absent Si-C bonds in SiOx coatings, creating a more rigid SiO₂-like cage structure. These findings provide crucial insights into structure-property relationships of silicon-based plasma coatings, essential for optimizing gas barrier functionality in applications like food packaging.Item type: Item , Special Issue: Plasma and Liquids—Fundamentals and Applications(Weinheim : Wiley VCH, 2025) Reuter, Stephan; Hamdan, Ahmad[no abstract available]Item type: Item , Characterization of a Gliding Arc Plasmatron for the Plasma Assisted Pyrolysis of Methane to Acetylene and Hydrogen(Weinheim : Wiley VCH, 2025) Böddeker, Simon; Göricke, Jan; Kogelheide, Bastian; Bibinov, Nikita; Purcel, Maximilian; Muhler, Martin; Mussenbrock, Thomas; Awakowicz, PeterA gliding arc plasmatron (GAP) is used for the production of hydrogen and acetylene via plasma-assisted methane pyrolysis. The working gas consists of argon with variable admixtures of methane. By applying camera measurements and optical emission spectroscopy the temperatures and electron density inside the GAP are measured. Two temperature regions are determined: the filamentary plasma, with 3470–5960 K, and a diffuse region characterized by black body emission of hot carbon containing dust at a temperature of 2230–2770 K. An analysis of the product gas stream shows a maximum methane conversion of 44% at a specific energy input of (Formula presented.) and selectivities towards hydrogen and acetylene between 25%–81% and 75%–89%, respectively.Item type: Item , Bubbling Water-Treating DBD Plasma Device Optimization Using Experimental and Computational Methods(Weinheim : Wiley VCH, 2025) Robinson, Conner D.; Sponsel, Nicholas L.; Stapelmann, KatharinaA dry air atmospheric pressure volume dielectric barrier discharge is employed to fix nitrogen in water. Producing nitrate for use as nitrogen fertilizer is the primary motivation. A 0D chemistry model is developed and informed by the electrical, and geometric characteristics of the device and the plasma gas temperature. Modeled ozone and nitrate densities are compared to those measured experimentally in the plasma effluent and treated liquid for a range of gas temperatures. Modeled and measured ozone densities are in good agreement; however, the model lacks the liquid chemistry to properly represent the measured nitrate density. A gas temperature-based shift from ozone to (Formula presented.) producing regimes is observed in both experiment and model, and the reactions responsible are evaluated.