Plasma Chemistry and Plasma Processing最新文献

A multiple-capillary Ar plasma jet was successfully generated by an advanced dielectric barrier discharge reactor. The reactor consisted of four quartz capillaries arranged separately and covered by two ring-shaped electrodes, which were isolated by a liquid dielectric. The advantages of the reactor included less Ar consumption (ranging from 1 to 3 L/min to obtain a total cross-sectional area of four individual plasma flow components of 3.14 mm² at the capillary orifices) and low gas temperatures (not exceeding 40 °C). The obtained temperature is suitable for implementing various biomedical applications such as wound healing, dental treatment, and cancer therapy. Furthermore, the plasma jet spread when it interreacted with dielectric materials or skin, resulting in an enlarged effective plasma treatment area of approximately 8 mm². Analysis of optical emission spectra of the plasma jet indicated the existence of several reactive species, suggesting that the plasma device holds potential for biomedical applications and material surface treatments.

Dielectric barrier discharges (DBD) are often used for gas conversion, such as carbon dioxide splitting, volatile organic compound removal or ozone generation. Due to the tiny plasma filaments in DBD discharges, efficient mixing of the gas flow with the plasma is essential. This is studied by using a surface dielectric barrier discharge (sDBD) with an electrode design similar to plasma actuators to optimize plasma-flow interaction. The flow pattern has been measured by Schlieren diagnostics and compared to a fluid dynamic simulation. Gas conversion efficiency has been tested by monitoring the conversion of 0.7% CO(_2) admixed to an N(_2) gas stream via infrared spectroscopy in the exhaust. The actuator design of the electrodes induces a significant plasma force on the fluid, which results in the formation of vortices above the electrodes, as reproduced in the simulation. It is shown that the height of the vortices created in the velocity field can characterize the mixing process, which dominates the conversion efficiency of carbon dioxide at different gas flow rates.

The application of Low-Temperature Plasmas has shown great potential as an effective and alternative tool for microbial inactivation in recent years. Nevertheless, further investigations are required to fully understand the possible factors influencing these processes. The present study aims to investigate the effectiveness of square wave modulated Volume Dielectric Barrier Discharge on the direct inhibition of conidial germination in five different fungal species, various discharge conditions, and medium composition. The five different fungal species used were Botrytis cinerea, Monilinia fructicola, Aspergillus carbonarius, Fusarium graminearum, and Alternaria alternata. On water agar, the inhibition of Botrytis cinerea was influenced by the applied voltage, which mainly reflects the uniformity of the treatment. Under the selected voltage condition, the inhibition increased with treatment duration and decreased with fungal spore complexity. B. cinerea and M. fructicola, with unicellular conidia and low melanin content, showed similar behaviour and high sensitivity to the treatment. F. graminearum and A. alternata, both having multicellular conidia, were more resistant to the plasma treatment and showed different sensitivity likely due to different content in melanin. However, after 1 min of treatment, complete inhibition of conidial germination was achieved for all the tested species. Inhibition of A. carbonarius conidia on different agarized media containing dextrose or malt extract was influenced by the complexity and composition of the medium, being potato dextrose agar that more hindered the plasma efficacy. Each medium exhibited a different electrical response studied by Electrical Impedance Spectroscopy and morphology observed by Scanning Electron Microscopy images. These differences translated into a different response to the applied electrical field, influencing plasma generation and uniformity.

There exist always some H₂S in natural gas. The industrialized process for H₂S removal is an energy intense process and must be applied in a large scale. An alternative process is needed. Herein, we report a removal of H₂S from a model natural gas mixture with methane, ethane and propane by dielectric barrier discharge (DBD), with which the dielectric (quartz) is frosted and coated with a layer of zeolite imidazole framework-67 (ZIF-67) nanoparticles. Compared to the DBD without coating, the average electric field as well as the mean electron energy of the DBD with ZIF-67 coating are higher at the same specific energy input (SEI), leading to a high H₂S conversion of 75.4% with the limited conversion of methane (less than 2%). No conversions of other low alkanes can be detected. This provides a potential way for the H₂S removal from the natural gas sources in the remote or isolated region.

Graphical abstract

Ammonia synthesis via non-thermal plasma presents advantages over the Haber–Bosch process, particularly for small-scale and distributed operations powered by intermittent electricity from renewable energy sources. We designed and characterized a membrane Dielectric-Barrier Discharge (mDBD) reactor for ammonia synthesis from nitrogen and hydrogen. The reactor used a porous alumina membrane as dielectric barrier and as distributor of H₂. This arrangement enabled greater residence time for N₂ decomposition together with greater H₂ availability in the reaction zone, as assessed by a computational thermal-fluid model. We evaluated the reactor's operation with membranes of 0.1, 1.0, and 2.0 µm pore size and porosities between 25 and 51%, and also in conventional DBD mode using a non-porous dielectric. The experimental characterization of the reactor encompassed electrical, optical, and spectroscopic diagnostics, as well as Fourier-Transform Infrared Spectroscopy to analyze gas products, as function of driving voltage. The results show that both, ammonia production and power consumption vary inversely with the product of membrane pore size and porosity. The highest energy yield of 0.25 g-NH₃/kWh was obtained with the membrane with 1.0 µm pore size and 35% porosity, whereas the maximum yield under conventional DBD operation was three-times lower. Our findings demonstrate that the use of a membrane dielectric can enhance the performance of DBD-based ammonia synthesis.