Plasma Chemistry and Plasma Processing最新文献

An experimental and numerical study was conducted on the polymer ablated arc with an electrode configuration of a one-side gas flow outlet model. The polymers used for molded case circuit breaker and gas circuit breaker, such as PA6, POM, and PTFE, were compared. In the experiment, the polymer ablated arc characteristics of arc voltage, arc energy, and mass loss of polymer by ablation were measured. In the numerical calculation, an electromagnetic thermofluid simulation for polymer ablated arc was conducted using a calculation model of similar structure but without using empirical values. In the model used, the polymer ablation was treated as the pyrolytic ablation rather the photodegraded ablation because the arc plasma was definitely in contact with the polymer. The comparison of both experiment and numerical simulation results revealed the relationship between arc energy and mass loss of polymer by ablation, and these values agreed well. Therefore, the numerical simulation model with pyrolytic ablation developed was indicated to be valid for predicting the polymer ablated arc with plasma-polymer contact.

The rising demand for precision optics widely employed in ground and space-based astronomical instruments and other scientific instrumentation requires highly efficient advanced fabrication methods. Due to complex-shaped fused silica substrate surfaces like freeform or aspheres with strong curvatures or very small-sized components, a novel non-contact medium-pressure plasma-based method is developed to finish optical components. The present study critically compares the polished optical surfaces of a prism with a medium-pressure plasma process and wet chemical etching to provide insight into their smoothing. The results show that surface roughness (R_a) increases from 0.54 to 2.61 nm and 0.53 to 0.57 nm at 5 and 20 mbar total pressures, respectively, using a plasma process without surface contamination. However, wet chemical etching increases surface roughness (R_a) from 0.52 to 15.9 nm. The substrates' surface morphology, elemental composition, and surface topography are analyzed using FESEM, EDX, and AFM. Moreover, subsurface improvements are analyzed using Raman spectroscopy analysis.

Cold atmospheric plasma (CAP) has gaining potential, and very effective to curb or deactivate the various microorganisms such as bacteria and virus. Lately, the major outbreak SARS-CoV-2 infection has affected humanity largely with added complexity of its ability to mutate to variants such as Omicron. We have earlier shown the effectiveness of CAP on SARS-CoV-2 spike protein and, in this study, we have evaluated the effectiveness of CAP to deactivate Omicron. We studied the ability of the binding of Angiotensin converting Enzyme Protein (ACE2) protein to the plasma treated spike S1-S2 protein and spike Receptor binding domain (RBD) using Cold atmospheric plasma direct treatment as well as Plasma activated water (PAW). Results have shown the binding efficiency of Omicron spike protein to ACE2 decrease with increase in treatment time with both direct treatment and PAW as evidenced using spectroscopic techniques. The reactive species (RONS) play a major role in the efficient deactivation of the binding of ACE2 to the Omicron spike protein. Correspondingly, the comparison between the efficiency between direct treatment and PAW has also been discussed.

Oxygenates production from the partial oxidation of liquid fuel is required for a cleaner combustion. The effect of Mn/Fe ratio was investigated to improve the oxygenates formation via plasma catalytic n-C₅H₁₂ partial oxidation over FeMn/Al₂O₃ catalyst. The oxygenates selectivities exhibited a volcano shape with the Mn/Fe ratio and the highest value of 69% was obtained at Mn/Fe ratio of 7/3. The oxygenates selectivities were dominated by both the acidity and active oxygen species of catalyst, which could be tuned by Mn/Fe ratio. A close relationship between oxygenates selectivities, acidity, and active oxygen species of catalyst was established. The higher the active oxygen species content and the lower the acidity, the higher the oxygenates selectivities.

Experimental investigations of n-butane oxidation under atmospheric-pressure plasma conditions and in He-dilution have provided detailed information on the power-dependence of the conversion of (text {C}_{4}text {H}_{10}) into CO and (text {CO}_{2}) at 450 K surface temperature. The rf-plasma discharge has been equipped with a (text {MnO}_{2})-catalyst, and a significant impact on the reaction chain due to the presence of the catalyst surface could be observed. We report on ongoing data-based model development. Recently, a reaction kinetic model has been published, which agrees well with the experimental data (Stewig et al. in Plasma Sources Sci Technol 32:105006, 2023). However, that model could not clearly identify the main mechanisms in the interaction of plasma and catalyst. We show that various models can be found that explain the data similarly well. Detailed sensitivity analysis shows that only a maximum of three parameters can be identified in all the models considered for the currently limited data. Despite this limitation, we intend to continue the data analysis using more general models and introduce possible surface effects. Such unified models simultaneously describe the experimental data from both measurements with and without catalyst using a single set of physical parameters. To evaluate the hypotheses, we present numerical results for certain ranges of experimental parameters, which, in a subsequent experimental verification, allows to exclude or confirm one or another model.

Understanding the individual effects of species in plasma activated water (PAW) is indeed necessary for its selective application as an antimicrobial agent. The current study describes a setup and a methodology to generate species-specific high strength PAW at neutral pH. Three types of PAW i.e., ROS-rich PAW (Reactive Oxygen Species-rich Plasma Activated Water), RNS-rich PAbW (Reactive Nitrogen Species- Rich Plasma Activated buffer Water) and hs-PAbW (High strength Plasma Activated buffer Water) were generated in the developed set-up, the concentration of species was measured, shelf-life studies under ambient condition were carried out and each water type was studied for its antimicrobial activity. Results show that, after 60 min of activation, hs-PAbW had ROS and RNS concentrations of 215 mg/l and 650 mg/l respectively. The ROS-rich PAW had ROS and RNS concentration of 218 mg/l and 0 mg/l respectively. The RNS-rich PAbW had ROS and RNS concentration of 16 mg/l and 858 mg/l respectively after 60 min of activation. Antimicrobial studies showed that individual species i.e., high concentrations of ROS alone and high concentrations of RNS alone, were ineffective in achieving microbial degradation, whereas hs-PAbW containing high concentrations of both ROS and RNS showed significant antimicrobial effect. This study marks an important step in generating high concentrations of species-specific PAW, which is crucial to understand the mechanistic pathways of bacterial death in PAW systems.

We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve (sim )4-log reduction in Escherichia coli population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O(_3), NO(_2), N(_2)O and N(_2)O(_5). The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the E. coli is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O(_3), NO(_2), and N(_2)O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments.

New collision integrals and transport cross sections for O((^{3})P)–O((^{3})P) interaction are reported in the 300–30000 K range. Those values are based on a new set of potential energy curves (PECs) calculated with the multireference configuration interaction method. The results of the classical and semiclassical WKB (Wentzel–Kramers–Brillouin) methods are compared, excellent performance of the classical approach is shown (discrepancy much lower than 1% even at room temperature). In particular, the classical and WKB methods agree very well for the repulsive potentials effectively reducing overall uncertainty.