Plasma Chemistry and Plasma Processing最新文献

Pulsed nature of plasma offers an efficient way to control film chemistry during plasma polymerization using very low average power. The pulsed plasma approach helps in introducing and retaining reactive surface functional groups at controlled densities, provides an efficient way of molecular tailoring of surfaces. We have, in the present work, investigated the control of –OH and –COOH groups within plasma-polymerized methacrylic acid (PPMAA) films synthesized using pulsed plasma technique. These groups are very important to attach biomolecules for a variety of applications. We demonstrate that the film chemistry is different for the films deposited at the same duty cycle of the pulse but with different ON and OFF times that influence the deposition rate. These films are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, surface profilometer, AFM and contact angle measurement. XPS and FTIR studies confirmed incorporation of –OH and –COOH groups onto the film surface. Contact angle results reveal that contact angle decreases from 64º to 41º for 1/15 and 3/90 ms pulse respectively revealing hydrophilic nature of the films. Thickness of the films have been varied from 360Å to 2600Å for CW and 3/30ms pulse respectively, while keeping deposition time 15 min constant. These results illustrate that pulsed plasma polymerization can be effectively utilized to tailor film chemistry for various applications.

N(_2)-H(_2) discharges are systematically studied using a coaxial dielectric barrier discharge reactor for ammonia synthesis by means of mass spectrometry, electrical characterization and high-resolution emission spectroscopy. The influence of packing is investigated by accommodating chemically inert SiO(_2) beads in the discharge volume from 920 to 13 mbar. Above 275 mbar, the discharge is dominated by filaments associated with intense microdischarges, whereas at lower pressures, the plasma becomes diffuse and occupies a large volume. In presence of packing, the intensity of the microdischarges at 920 mbar are strongly suppressed, while the electrical and emission properties of the diffuse plasma remain largely unaffected. The absence of intense microdischarges in the diffuse mode at low pressures eliminates important NH(_3) dissociation channels. Decreasing the pressure below 100 mbar leads to a significant increase in [NH(_3)] with SiO(_2) beads. This is attributed to both an increase of E/n, which favours H(_2) and N(_2) dissociation, and consequently to an increase in plasma-surface reactions involving H and N towards ammonia formation. Investigations at 50 mbar reveal that introducing SiO(_2) beads in contact with the plasma has a more limited impact on [NH(_3)] than at 920 mbar. The emission spectra are dominated by the second positive system of N(_2), first negative system of N(_2^+), and H(_{alpha }), with no evidence of excited NH(^*). The rotational temperature of N(_2)(C) is mostly affected by [N(_2)] in [H(_2)] in the empty reactor at 920 mbar, reaching about 808 K at 75 vol.% N(_2). With packing or at 50 mbar the rotational temperature remains at (approx 400,)K. For all tested conditions, the vibrational temperatures of N(_2)(C) lie in the range of (3500-3900,text {K}).

This paper presents the experimental results of the decomposition products of C₅F₁₀O/N₂ in AC corona discharge under different trace H₂O contents. The decomposition products are detected by electron attachment mass spectrometry. A needle-plane electrode is installed in the gas chamber filled with C₅F₁₀O/N₂ mixture to simulate corona discharge. In the detection method of electron attachment mass spectrometry, negative ions are detected by mass spectrometry. By tracing the formation pathways of negative ions, the corresponding decomposition products can be determined. The trace H₂O contents include 800ppm, 1600ppm and 3000ppm. A total of 24 decomposition products are detected, including CF₄, C₂F₄, C₃F₆, C₃F₈, C₄F₆, C₄F₈, C₄F₁₀, C₅F₁₀, C₆F₁₂, CF₂O, CF₄O, C₂F₄O, C₂F₆O, C₃F₄O, C₃F₆O, C₃F₈O, C₄F₆O, C₅F₈O, CHF₃O, C₃HF₅, C₃HF₇, CF₃N, C₂F₃N and C₂H₂F₃NO. The variation trends of the decomposition products under three trace H₂O contents are investigated. By comparing the decomposition products in C₅F₁₀O/N₂ mixture with and without trace H₂O at 10 h, the results show that the addition of trace H₂O can promote the decomposition of C₅F₁₀O/N₂ mixture. The possible generation pathways of the decomposition products in corona discharge are also determined to discover the formation mechanism of the decomposition products.

In the automotive sector, the shift from combustion engines (gasoline and diesel) to electric powertrains, such as battery and hybrid electric vehicles, is advancing. By contrast, diesel engines remain the primary power source for marine vessels. Approximately 95% of marine propulsion systems rely on diesel and other combustion engines such as gas-fueled units. This share is unlikely to decline in the near future, given that batteries are not well-suited for long-range ocean voyages. Consequently, diesel engines are the primary power sources for ships. However, emissions such as nitrogen oxides (NO_x) and particulate matter (PM) must be reduced, even for low-emission diesel engines fueled with non-sulfur gas oil or light oil, to realize ultraclean operation. This study investigates aftertreatment strategies for low-emission diesel engines to realize an ultraclean exhaust that remains competitive with moving electric power sources. We propose an aftertreatment technology based on surface discharge-induced plasma. The proposed approach does not require additives such as urea. We successfully removed NO_x and hydrocarbons (HCs) from diesel engine exhaust gases by passing the exhaust gas through a plasma reactor at high exhaust gas flow rates. In addition, by measuring the concentrations of the exhaust gas components including NO, NO_x, CO, CO₂, total hydrocarbons, O₂, H₂O, O₃, and HNO₃ before and after plasma treatment, we examined the reaction of these components within the reactor. The results show that the removal efficiencies of NO_x and HC are 67% and 76%, respectively, at a specific energy of 143 J/L. PM and HCs are removed by oxidation with atomic oxygen species generated from O₃ and NO₂ produced by the surface-discharge plasma. NO_x is reduced through reduction reactions with the reducing components CO and HC. The experimental results show that it is necessary to operate the plasma reactor under conditions of low specific energy or low plasma power conditions to increase the removal efficiencies of NO_x and HC.

Amid concerns about the progress of climate change, the development of effective utilization technologies of carbon dioxide (CO₂) has gained significant attention as a means to sustainably reduce CO₂ concentration in the atmosphere. The reverse water-gas shift (RWGS) reaction (CO₂ + H₂ → CO + H₂O) using CO₂ and hydrogen (H₂) with a ratio of 1:1, which produces carbon monoxide (CO) employed as an essential feedstock in chemical industries, is a promising and practical strategy for effective utilization of CO₂. This study investigates experimentally the non-catalytic RWGS reaction using microwave discharge plasma at atmospheric pressure. The microwave discharge plasma can be generated using a rod-electrode-type microwave plasma source (MPS). The CO₂ conversion, CO selectivity, CO yield, and specific energy input (SEI) are then evaluated in terms of the average transmission power to the rod-electrode-type MPS at a constant flow rate. The highest CO₂ conversion of 55.9%, CO selectivity of 90.6%, and CO yield of 50.7% are achieved at the SEI of approximately 2.5 eV/molecule (equivalent to approximately 9.9 kJ/L). On the other hand, the highest energy efficiency for the CO yield of 10.6% was achieved at the SEI of approximately 1.6 eV/molecule (equivalent to approximately 6.5 kJ/L). The findings highlight the potential of microwave discharge plasma as a viable approach for promoting the non-catalytic RWGS reaction at atmospheric pressure, offering a novel pathway for efficient CO₂ utilization.

This study focuses on the plasma deposition of metal/polymer nanocomposite thin films at atmospheric pressure and low temperature. The synthesis process combines a dielectric barrier discharge (DBD) with the aerosol of a solution of a gold salt (i.e., tetrachloroauric acid trihydrate, HAuCl₄·3H₂O) in isopropanol. In particular, the solution is injected as an aerosol into a parallel-plate DBD fed with nitrogen and powered by a dual-frequency modulated (800 Hz/20 kHz) sinusoidal high voltage. The influence of the duty cycle (i.e., the ratio of high-frequency time to total cycle time) on the properties of the deposited layers is assessed, keeping constant the gold salt concentration in the aerosolized solution. The chemical composition, morphology, and optical properties of the deposited layers are determined using various characterization techniques, including attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, UV-Visible absorption spectroscopy, and scanning electron microscopy with energy dispersive X-ray spectrometry. It appears that increasing the duty cycle affects both the growth rate of the nanocomposite thin film and the efficiency in gold salt reduction into metallic nanoparticles, thereby influencing the plasmonic properties. Overall, these results offer new insights into the potential of using a single-step aerosol-assisted plasma process to deposit functional organic/inorganic nanocomposite thin films at atmospheric pressure.

In this study, Ar–(:{text{N}}_{2}text{O}) discharges sustained by a surfatron device operated at atmospheric pressure were investigated to elucidate their physicochemical behavior and potential for reactive oxygen and nitrogen species (RONS) generation through (:{text{N}}_{2}text{O}) decomposition. The addition of (:{text{N}}_{2}text{O}) to an argon plasma led to a shortening of the plasma column and the appearance of a diffuse afterglow region that extends to long distances (> 50 cm). Increasing (:{text{N}}_{2}text{O}) concentration results in suppression of the discharge filamentation, as well as to an increase in gas temperature, that exceeds 3000 K above 1.5% (:{text{N}}_{2}text{O}). Spectroscopic and thermometric analyses confirmed effective (:{text{N}}_{2}text{O}) dissociation and the formation of RONS in the discharge. The afterglow, characterized by long-lived metastables and excited argon, nitrogen, and oxygen species, exhibited progressively decreasing temperatures, reaching below 100 °C. Optical emission analysis in this zone revealed rich (:text{A}text{r}), (:text{N}), (:text{O}), (:text{N}text{O}), (:text{O}text{H}), and (:text{N}text{H}) spectra, from which dissociation pathways and kinetic mechanisms have been proposed. A simplified kinetics scheme to elucidate the behavior of these plasmas is proposed, and the results are compared to those obtained with Ar–(:{text{N}}_{2}) plasmas and postdischarges. In addition, mass spectrometry suggests (:{text{N}}_{2}text{O}) decomposition preferentially takes place through nitrogen-oxygen bond breaking, yielding (:{text{N}}_{2}), (:{text{O}}_{2}), and (:{text{N}text{O}}_{text{x}}) products at the gas exhaust.

Tin contamination in extreme ultraviolet lithography (EUVL) optics can be partially removed from radical-mediated reactions in hydrogen plasmas by formation of the volatile produce stannane (SnH₄). Using density functional theory (DFT) and transition state theory (TST), we examine two competing SnH₄-SnH radical pathways–channel 1 (Sn₂H₃ + H₂) and channel 2 (Sn₂H₅)--that influence downstream tin deposition. Distinct bonding mechanisms render channel 1 endothermic and tunneling-sensitive, while channel 2 is exothermic, spontaneous, and kinetically dominant under process conditions. These findings provide molecular-level guidance for predicting plasma-driven tin species fluxes to optical surfaces, offering a basis for optimizing contamination control in the EUVL systems.

A novel plasma-assisted electrospray device has been proposed, enabling the generation of charged nanodroplets and the incorporation of chemically active species, e.g., hydroxyl radicals (OH radicals, OH), produced during plasma–liquid interactions at the droplet surface. We particularly investigated the influence of background gas conditions (N₂/O₂ ratio) on the droplet number concentration, droplet size distribution, and the estimation of OH production in droplets by a chemical probe method using disodium terephthalate (NaTA) as the treatment solution. Furthermore, we analyzed changes in the plasma emission spectrum at the Taylor cone tip. The plasma emission and the shape of the Taylor cone varied with O₂ concentration, which significantly affected the droplet number concentration. These changes were evaluated using two stabilization indices that consider the inhibition of electrostatic spraying by discharge and the spray duration, thereby revealing the macroscopic droplet spraying process. When droplets were exposed to the treatment solution, the detected OH amount increased with increasing O₂ concentration. The detected OH is likely contained within the droplets, and despite the droplet transport time being much longer than the OH lifetime, OH was detected, suggesting that OH may have been regenerated within the droplets during their transport. It is likely that OH radicals are mainly generated through the peroxone process, which involves the reaction between O₃ and hydrogen peroxide (H₂O₂). This can be explained by the fact that the O₂ concentration dependence of the gas-phase O₃ concentration shows a similar trend to that of the HTA concentration.

As the primary method for industrial ozone (O₃) synthesis, atmospheric-pressure dielectric barrier discharge has attracted extensive attention with regard to its energy efficiency. Researchers have tried using ns-pulsed or pulse-modulated AC power supplies to reduce gas temperature and enhance efficiency. However, ns-pulsed overvoltage breakdown facilitates quenching particles that accelerate O₃ decomposition, while pulse-modulated AC’s non-short discharge duration reduces cooling efficiency. Additionally, the exorbitant price of high-frequency ns-pulse power supplies diminishes overall system efficiency. This work proposes a novel pulsed AC power supply to circumvent these limitations. The cost of this supply is comparable to traditional continuous AC power supplies. By shortening the discharge duration while suppressing quenching particles, it achieves an ultrahigh O₃ synthesis energy efficiency of 1020 ± 186 g/kWh. Compared to continuous AC-driven discharge, it reduces power consumption by 68–94%, rotational temperature by 118–161 K, and the overall intensities of quenching transient particles of OH by 19–23% and N₂* by 32–42%. These improvements enable high O₃ synthesis efficiency. When generating O₃ at 240–280 ppm, it cuts energy consumption by approximately 94%, and maintains N₂O proportion at 1.5–2.2%. These findings provide new insights into optimizing the performance of ozone generators from a power supply perspective.