Plasma Chemistry and Plasma Processing最新文献

Plasma technology has emerged as a promising approach for regulating grain seed germination, offering dual effects of promotion and inhibition depending on treatment parameters. This review synthesizes mechanisms by which cold plasma (CP) and plasma-activated water (PAW) influence seed physiology. Reactive oxygen and nitrogen species (RONS) generated during plasma treatment modify seed coat hydrophilicity through etching, enhance water uptake, and alter metabolic pathways. Moderate RONS levels stimulate antioxidant systems, hormone balance (e.g., GA/ABA ratio), and enzyme activities (e.g., amylase, superoxide dismutase), accelerating germination. Conversely, excessive RONS induce oxidative damage, inhibit enzyme function, and impair DNA/protein integrity. PAW, enriched with nitrate, nitrite, and H₂O₂, further enhances germination by improving nutrient absorption and microbial decontamination. Notably, plasma efficacy varies with seed type, treatment duration, voltage, and gas composition. Short-term, low-dose CP promotes germination in crops like maize, wheat, and rice, while prolonged exposure or high-intensity treatment suppresses it. CP also mitigates abiotic stresses (e.g., drought, salinity) by enhancing stress-responsive pathways. Despite advantages such as residue-free processing and scalability, challenges persist, including equipment costs, inconsistent treatment efficacy, and unresolved safety concerns regarding long-term environmental and health impacts. Future research should prioritize elucidating molecular interactions, optimizing protocols for diverse crops, and advancing scalable plasma systems. With further refinement, plasma technology holds significant potential to revolutionize sustainable agriculture by improving seed storage, stress resilience, and crop productivity.

Film cooling shows significant potential for mitigating the “blackout” effect caused by plasma sheaths. In this paper, the influence of cooling gas film on the key characteristic parameters (electron density and collision frequency) and electromagnetic transmission characteristics of the plasma sheath are studied by controlling the shoulder of the aircraft to spray cooling gas to simulate energy injection and absorption. The results show that under hypersonic flow conditions, the electron density increases due to the dissociation of the counterflow jet medium and diffuses downstream over the vehicle body. The cooling gas film can be formed on the target wall by spraying CO₂ and N₂ through the shoulder, the electron density and plasma frequency on the wall decreases. Notably, the plasma collision frequency increases to varying degrees due to the dissociation of the injected particles. Under N₂/CO₂ film cooling, the Maximum attenuation intensity of electromagnetic wave is reduced by 15dB, the resonant frequency of electromagnetic wave and plasma sheath is increased. This study provides valuable insights for designing physical and chemical interventions to regulate the spatial distribution of plasma and the research of anti-black barrier communication.

AlN plasma emission behavior in argon atmosphere has been investigated by infrared nanosecond laser using optical emission spectroscopy (OES) diagnostics. The effect of argon pressure on the time–space evolution of the plasma composition, as well as the dependence of electron number density, has been studied. To investigate the impact of the ambient gas nature on the temporal behavior of plasma species, we performed space and time resolved emission spectroscopy. Time of flight (TOF) measurements of neutral and ionized Al, N, and Ar species revealed the presence of double and triple structure, depending on the ambient gas nature. In an argon atmosphere, slower components of Al and N exhibited backward motion. The faster Al⁺ component unaffected by the surrounding gas and followed a propagation profile like that observed in vacuum. The kinetics of all plasma species were investigated.

This paper aims to advance the achievement of industrial-scale efficient thermal decomposition of pulverized coal into acetylene utilizing arc plasma. A comprehensive physical model, incorporating detailed reaction mechanisms, has been constructed to elucidate the multi-field coupled interaction mechanism between coal particles and hydrogen plasma jets, alongside the millisecond-scale pyrolysis process. The core functionality of this model lies in elucidating the regulatory mechanisms through which distinct high-temperature zones within the reactor govern the elementary reactions pertaining to acetylene and tar. Building upon this, it further proposes a flow mixing optimization strategy: enhancing the contact area and duration between the > 2500 K region and pulverized coal. Additionally, the model clarifies the synergistic effects of the spatiotemporal characteristics of particle devolatilization in the main flow and near-wall regions under the tangential circular mixing regime on energy efficiency. Furthermore, by optimizing reactor structural parameters such as diameter, energy efficiency can be elevated to approximately 16%. This model establishes a robust framework for numerical simulations of future industrial-scale thermal plasma coal pyrolysis systems and offers pragmatic guidance for the industrialization of this technology.

Massive production and consumption of ground tire rubber (GTR) for transportation have led to significant waste rubber accumulation, posing a serious environmental threat. Rubber devulcanization technologies, as a promising strategy for rubber recycling, still face several challenges, including high consumption, pollution concerns. This study proposes an innovative method for rubber devulcanization using dielectric barrier discharge (DBD) plasma. Experimental results demonstrate a significant reduction in crosslink density, decreasing from 2.1 × 10⁻⁴ mol/cm³ to 0.8 × 10⁻⁴ mol/cm³, after plasma treatment at a discharge voltage of 18 kV for 30 min. This reduction is accompanied by a decrease in gel content from 96.79 to 90.54%, indicating the effective cleavage of S-S and C-S bonds within GTR. Notably, after plasma treatment, the tensile strength and elongation at break of the regenerated rubber reached 10.2 MPa and 357.7%, respectively, meeting the standards for high-grade rubber. These mechanical properties meet the standards for high-grade rubber, rendering the devulcanized rubber suitable for reuse in industrial manufacturing processes. However, when the discharge voltage surpasses a critical level, the electron energy attains a magnitude sufficient to cause extensive structural damage to the rubber backbone of GTR. Consequently, this degradation results in a significant reduction in the molecular weight of the regenerated GTR, which ultimately leads to a decrease in both tensile strength and elongation at break. Based on a comprehensive analysis of experimental data and characterization results, a plausible mechanism for plasma-assisted devulcanization is proposed, highlighting the significant potential to enhance environmental sustainability and support circular economy initiatives.

A new discharge configuration for nanoparticle synthesis has been investigated in this work: microsecond discharge of liquid with aluminium pellets in the interelectrode gap. This plasma-based method enables efficient synthesis of high-yield aluminium hydroxide nanoparticles. We investigated nanoparticle synthesis using two conductivity liquid: distilled water (1 µS/cm) and (ii) and NaCl solution (1 mS/cm). The nanoparticle maximum production rate of our technique was ∼12 g/h. We used transmission electron microscopy and X-ray diffraction analysis to characterize the synthesized material. The linear size of the nanoparticles ranged from a few units to 600 nm, and the main crystalline phases of aluminium hydroxide were byerite and gibbsite.

Dielectric barrier discharge (DBD) plasma technology holds great potential for soil remediation. However, the coupling mechanisms among plasma kinetics, soil properties, and chemical additives remain unclear. This study developed a numerical model integrating nanosecond-scale discharge, second-scale radical reactions, and pollutant migration over minutes to hours, analyzing the effects of pH, porosity, soil thickness, and ionic additives (CO₃²⁻, Fe²⁺) on atrazine degradation. Simulation results indicate that CO₃²⁻ competitively consumes hydroxyl radicals (⋅OH), reducing their concentration while promoting ozone (O₃) formation, thereby altering the degradation pathway. Fe²⁺ catalyzes ⋅OH generation via Fenton-like reactions, achieving maximum degradation efficiency at pH ≈ 8.5–9.0 and Fe²⁺ = 5 × 10⁻³ mol/m³, whereas excessive Fe²⁺ (> 0.01 mol/m³) consumes radicals, diminishing degradation effectiveness. Long-term analysis reveals that the inhibitory effect of CO₃²⁻ stabilizes over time, whereas the enhancement effect of Fe²⁺ is more pronounced in the initial phase. Soil porosity and thickness determine plasma penetration depth, thereby influencing long-term degradation efficiency. This study elucidates the short-term and long-term effects of CO₃²⁻ and Fe²⁺ on atrazine degradation, highlighting the critical role of soil structure in long-term remediation and providing theoretical guidance for optimizing DBD plasma remediation technology.

Graphical Abstract

Here is a visually compelling infographic highlighting the breakthrough research in DBD plasma soil remediation. It includes the key elements of the study, such as the effects of CO₃²⁻ and Fe²⁺ ion additives on atrazine degradation, and visually presents the impact of soil heterogeneity, plasma chemistry, and free radical reactions. This infographic can help in clearly communicating the research findings.

CH₄ reforming with CO₂ was investigated using nanosecond pulsed DBD plasma, focusing on pulse parameters (pulse width and repetition frequency), discharge power, residence time and molar ratios on reaction performance. Furthermore, the impact of oxygen addition to the feed gas mixture was evaluated. At a constant power of 16 W and flow rate of 40 ml. min^-1, the increase in pulse width from 150 ns to 175 ns enhanced CH₄ conversion from 18.6 to 21.1%, while CO₂ conversion remained relatively stable, around 8.0%. Notably, the selectivity of products remained constant despite these changes, the main product being CO with a selectivity close to 50%. Increasing the frequency resulted in improved conversions, with optimal CO₂ and CH₄ conversions of 8.0% and 21.1%, respectively at 10 kHz. Methanol was identified with a low selectivity of 1.8% at 10 kHz. By varying the oxygen percentage, a marked shift in product selectivity from hydrocarbons to CO was observed. At 20% oxygen content in the feed gas, a CO selectivity of nearly 85% was achieved, with a methane conversion of 33.1%. Nanosecond pulsed plasma discharge with O₂ favors the partial oxidation of methane. A study of the effect of residence time revealed significant differences in reaction pathways between oxygen-free and oxygen-containing mixtures. Without oxygen, propane emerges as a primary reaction product when using a pure mixture of CH₄ and CO₂. However, when oxygen is present, the formation pathway for propane changes, with ethane serving as an intermediate. To our knowledge, this has never been reported in the literature.

The twin torch arc system currently mainly confronts issues such as unstable discharge and rapid anode ablation. In this work, we designed a rod cathode-tubular anode twin torch arc system. The influence of anode structure parameters and operating parameters on the arc discharge characteristics was systematically investigated. Research indicated that the tubular anodes had a stronger arc confinement effect compared to the rod cathode, which affected the symmetry of dual jet. There was a minimum gas flow requirement to sustain discharge stability, and the minimum gas flow increased with the increase in the anode’s inner diameter and depth. As the inner diameter and depth of the anode increased, the arc spot moved backward, thereby increasing the constraint length of the anode wall to the arc. This resulted in a higher average discharge voltage and reduced voltage fluctuations. However, it also raised the lower limit of the gas flow required to maintain stable arc discharge. Moreover, the cavity structure of the tubular anode induced a Helmholtz resonance phenomenon. The resonance frequency decreased with the increase of the anode inner diameter and depth, and it increased with the increase of current and the decrease of inlet gas flow. Compared to that of the rod-shaped anode, the ablation rate of the tubular electrode was significantly lower, which could reach to 4.5 × 10⁻¹¹ kg/C. This study may provide more basic data for the optimized design of twin torch arc system.

In this study, Ar-CO₂ submerged thermal plasma jet was generated using a novel 15 kW DC non-transferred hollow cathode torch to evaluate the efficiency of the thermal plasma system for the degradation of a 30% (v/v) tributyl phosphate in dodecane (TBP/DD). The plasma torch was characterized to understand its operational behavior under varying conditions, such as current-voltage (I-V) characteristics, arc voltage fluctuations, jet length, and UV radiation emission intensity at different Ar-CO₂ gas ratios. The TBP/DD organic solvent was introduced into the reactor along with water, forming two distinct phases: organic phase and aqueous phase. This two-phase mixture was then subjected to thermal plasma treatment for varying durations. The system demonstrated complete organic volume reduction, around 97.7% mineralization efficiency, and 90% phosphorus capture, thus highlighting the reactor’s significant potential for organic liquid waste degradation. Liquid chromatography-mass spectrometry (LC-MS) analysis of the aqueous phase was used to identify the degradation intermediates, providing insight into the chemical transformations during plasma treatment. The Fourier transform infrared (FTIR) spectrum of solid residues obtained at the end of the treatment revealed that carbonaceous compounds are the stable end products of the treatment process. The integration of these analytical techniques not only confirms the effective degradation of organic liquid waste but also elucidates potential degradation pathways and mechanisms underlying the degradation of organic waste in the Ar-CO₂ submerged thermal plasma system. These findings significantly advance the understanding of plasma-induced organophosphate breakdown, providing a foundation for optimizing thermal plasma systems in the treatment of hazardous organic contaminants.