Search Results (475)

This work explores microcombustion technologies enhanced by plasma-assisted combustion, focusing on a novel simulation model for a Y-shaped device with a non-premixed hydrogen-air mixture. The simulation integrates the ZDPlasKin toolbox to determine plasma-produced species concentrations to Particle-In-Cell with Monte Carlo Collision analysis for momentum and power density effects. The study details an FE-DBD plasma actuator operating under a sinusoidal voltage from 150 to 325 V peak-to-peak and a 162.5 V DC bias. At potentials below 250 V, no hydrogen dissociation occurs. The equivalence ratio fitting curve for radical species is incorporated into the plasma domain, ensuring local composition accuracy. Among the main radical species produced, H reaches a maximum mass fraction of 8% and OH reaches 1%. For an equivalence ratio of 0.5, the maximum temperature reached 2238 K due to kinetic and joule heating contributions. With plasma actuation with radicals in play, the temperature increased to 2832 K, and with complete plasma actuation, it further rose to 2918.45 K. Without plasma actuation, the temperature remained at 300 K, reflecting ambient conditions and no combustion phenomena. At lower equivalence ratios, temperatures in the plasma area consistently remained around 2900 K. With reduced thermal power, the flame region decreased, and at Φ = 0.1, the hot region was confined primarily to the plasma area, indicating a potential blow-off limit. The model aligns with experimental data and introduces relevant functionalities for modeling plasma interactions within microcombustors, providing a foundation for future validation and numerical models in plasma-assisted microcombustion applications. Full article

To conquer the challenges of charge accumulation and surface flashover in epoxy resin under direct current (DC) electric fields, numerous efforts have been made to research dielectric barrier discharge (DBD) plasma treatments using CF₄/Ar as the medium gas, which has proven effective in improving surface flashover voltage. However, despite being an efficient plasma etching medium, SF₆/Ar has remained largely unexplored. In this work, we constructed a DBD plasma device with an SF₆/Ar gas medium and explored the influence of processing times and gas flow rates on the morphology and surface flashover voltage of epoxy resin. The surface morphology observed by SEM indicates that the degree of plasma etching intensifies with processing time and gas flow rate, and the quantitative characterization of AFM indicates a maximum roughness of 144 nm after 3 min of treatment. Flashover test results show that at 2 min of processing time, the surface flashover voltage reached a maximum of 19.02 kV/mm, which is 25.49% higher than that of the untreated sample and previously reported works. In addition to the effect of surface roughness, charge trap distribution shows that fluorinated groups help to deepen the trap energy levels and density. The optimal modification was achieved at a gas flow rate of 3.5 slm coupled with 2 min of processing time. Furthermore, density functional theory (DFT) calculations reveal that fluorination introduces additional electron traps (0.29 eV) and hole traps (0.38 eV), enhancing the capture of charge carriers and suppressing surface flashover. Full article

Molecularly imprinted polymers (MIPs) are synthetic polymers that mimic the functions of antibodies. Though MIPs are promising tools in various areas, achieving high selectivity in MIPs can be difficult. To improve selectivity, various approaches have been implemented; however, the role of polymerization methods or synthetic techniques in enhancing the selectivity of MIPs has not been studied and remains a crucial area for further research. MIPs are typically prepared from free radical reactions. Recently, we found that Dielectric Barrier Discharge (DBD) plasma can be used to initiate the polymerization of vinyl monomers. The DBD plasma method allows the monomers to associate with the template molecules and initiate polymerization with minimal disruption to the positioning of the monomers. We hypothesize that this could be a preferred method to prepare MIPs over the traditional radical reaction that may cause a disturbance of the pre-associated monomers on the templates for the polymerization. Chicken egg white serum albumin (CESA) was used as the template protein for the MIPs. Our results show that in all test conditions, approximately twofold improvement in selectivity was achieved, which is the primary performance metric for MIPs. This enhancement was evident across all categories, including MIPs prepared from various monomer combinations. Full article

Airborne pathogens, though a minor fraction of airborne particles, can cause infections, intoxications, or allergic reactions through respiration, dermal contact, or ingestion. The SARS-CoV-2 pandemic has underscored the significance of mitigating airborne microbial threats. Traditional air ionization methods, such as dielectric barrier discharge and metal tip corona discharge, produce ozone, a reactive and potentially harmful byproduct. However, carbon-fiber ionizers (CFIs) generate high concentrations of ions with minimal ozone production, making them a safer alternative. Operating at voltages below 5 kV, CFIs are more efficient than their metallic counterparts. This review focuses on the antimicrobial efficacy of CFIs, which produce unipolar ions that can disrupt microbial membranes, leading to cell death. Compared to ultraviolet light sterilization, CFIs are cost-effective and suitable for small spaces. The literature review highlights the need for comprehensive studies to evaluate the real-world application and effectiveness of CFIs. Many existing studies are limited by small-scale testing and insufficient data reporting, complicating comparative analyses. Our work aims to provide a detailed perspective on CFIs, examining their impact on various microorganisms, ion efficacy, ionization outcomes, and ozone generation levels. By addressing these aspects, the review seeks to offer an updated understanding of CFIs’ antimicrobial capabilities and to identify limitations in current research, paving the way for more informed and effective air purification strategies. Full article

To investigate the effect and mechanism of plasma-activated water (PAW) on Aspergillus niger, PAW was prepared using a needle array–plate dielectric barrier discharge plasma system. The concentrations of long-lived reactive oxygen and nitrogen species (RONS), namely, H₂O₂, NO₂⁻, and NO₃⁻, in the PAW were 48.76 mg/L, 0.046 mg/L, and 172.36 mg/L, respectively. Chemically activated water (CAW) with the same concentration of long-lived RONS was also prepared for comparison. A. niger A32 was treated with PAW and CAW. After treatment, the treated strains were observed and analyzed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to screen probable mutants. The results indicated that the pH, conductivity, and ORP values of PAW were 2.42, 1935 μS/cm, and 517.07 mV, respectively. In contrast, the pH and ORP values of CAW were 6.15 and 301.73 mV, respectively, which differed significantly from those of PAW. In addition, the conductivity of CAW showed no change. SEM and TEM analyses revealed that A. niger A32 treated with CAW exhibited less damage compared with the control. In contrast, A. niger A32 treated with PAW showed significant shrinkage, deformation, and exudate attachment over time. Following PAW treatment, after four passages, a high cellulase-producing stable mutant strain A-WW5 was screened, exhibiting a filter paper enzyme activity of 29.66 U/mL, a cellulose endonuclease activity of 13.79 U/mL, and a β-glucosidase activity of 27.13 U/mL. These values were found to be 33%, 38%, and 2.1% higher than those of the original fungus sample, respectively. In total, 116 SNPs and 61 InDels were present in the genome of the mutant strain A-WW5. The above findings indicate that the impact of PAW on A. niger is not only attributed to long-lasting H₂O₂, NO₂⁻, and NO₃⁻ particles but also to other short-lived active particles; PAW is expected to become a new microbial breeding mutagen. Full article

Dielectric barrier discharge plasma actuators have recently become desirable devices for simultaneous flow control and ice mitigation applications, with particular interest in wind turbines operating in cold climates. Considering the potential of plasma actuators for these specific applications, it is necessary to deeply understand the thermal effects generated by the plasma-induced flow to proceed with further optimizations. However, due to the local high electric field and high electromagnetic interference generated, there is a lack of experimental studies on the topic. The current work implements an in-house experimental technique based on the background-oriented schlieren principle for plasma-induced flow thermal characterization. Since this technique is based on optical measurements, it is not affected by the electromagnetic interference issues caused by the plasma discharge. A detailed experimental analysis is performed on a conventional Kapton actuator exploiting the relation between the actuator surface temperature and the induced thermal flow. The influence of the input voltage and the transient plasma-induced flow thermal behavior is analyzed. The results demonstrate that plasma actuators are fast response time devices that can heat the adjacent medium in less than a second after starting the operation. Full article

Nonthermal processing can change and improve the composition of food. This study examines the impact of cold plasma technology—glow discharge, dielectric barrier discharge (DBD), and ultrasound (US)—on the bioaccessibility of ascorbic acid (vitamin C) and total phenolic compounds (TPCs) in orange and cashew apple juice after simulated digestion. The juices were treated by DBD plasma for 20 min at three different frequencies (50, 500, and 1000 Hz), glow discharge plasma at three synthetic air flow rates (10, 20, and 30 mL/min), and US at three potencies (183, 280 and 373 W/cm²) for 10 min. The nonthermal processing did not significantly reduce the levels of ascorbic acid in cashew apple juice. In contrast, the ascorbic acid levels either remained stable or increased by up to 80% for orange juice. The processing improved the bioaccessibility of total phenolic compounds (TPCs) in both juices, reaching 150% in cashew apple juice treated with US at 373 W/cm². Despite the decrease in the bioaccessibility of ascorbic acid in orange juice, the nonthermal processing notably enhanced this bioactive compound’s bioaccessibility by 10% to 20% compared to the control sample, highlighting the potential of nonthermal technologies to improve the nutritional quality of foods. Full article

The oxidation of multi-walled carbon nanotubes (MWCNTs) using cold plasma was investigated for their subsequent use as adsorbents for the removal of dyes from aqueous solutions. The properties of MWCNTs after plasma modification and their adsorption capacities were compared with pristine and chemically oxidized nanotubes. The modification process employed a reactor where plasma was generated through dielectric barrier discharges (DBD) powered by high-voltage nanosecond pulses. Various modification conditions were examined, such as processing time and pulse voltage amplitude. The degree of oxidation and the impact on the chemistry and structure of the nanotubes was investigated through various physicochemical and morphological characterization techniques (XPS, BET, TEM, etc.). Maximum oxidation (O/C = 0.09 from O/C = 0.02 for pristine MWCNTs) was achieved after 60 min of nanopulsed-DBD plasma treatment. Subsequently, the modified nanotubes were used as adsorbents for the removal of the dye methylene blue (MB) from water. The adsorption experiments examined the effects of contact time between the adsorbent and MB, as well as the initial dye concentration in water. The plasma-modified nanotubes exhibited high MB removal efficiency, with adsorption capacity proportional to the degree of oxidation. Notably, their adsorption capacity significantly increased compared to both pristine and chemically oxidized MWCNTs (~54% and ~9%, respectively). Finally, the kinetics and mechanism of the adsorption process were studied, with experimental data fitting well to the pseudo-second-order kinetic model and the Langmuir isotherm model. This study underscores the potential of plasma technology as a low-cost and environmentally friendly approach for material modification and water purification. Full article

The generation of ozone by dielectric barrier discharge (DBD) is widely used for water and wastewater treatment, the control of catalytic reactions, and surface treatment. Recently, a need for compact, effective, and economical ozone and reactive oxygen–nitrogen species (RONS) generators for medical, biological, and agricultural applications has been observed. In this study, a novel hybrid DBD (HDBD) reactor fulfilling such requirements is presented. Its structured high-voltage (HV) electrode allows for the ignition of both the surface and volume microdischarges contributing to plasma generation. A Peltier module cooling of the dielectric barrier, made of alumina, allows for the efficient control of plasma chemistry. The typical electrical power consumption of this device is below 30 W. The operation frequency of the DBD driver oscillating in the auto-resonance mode is from 20 to 40 kHz. The specific energy input (SEI) of the reactor was controlled by the DBD driver input voltage in the range from 10.5 to 18.0 V, the Peltier current from 0 to 4.5 A, the duty cycle of the pulse-width modulated (PWM) power varied from 0 to 100%, and the gas flow from 0.5 to 10 SLM. The operation with oxygen, synthetic air, and compressed dry air (CDA) was characterized. The ultraviolet light (UV) absorption technique was implemented for the measurement of the ozone concentration. The higher harmonics of the discharge current observed in the frequency range of 5 to 50 MHz were used for monitoring the discharge net power. Full article

SF₆ is a strong greenhouse effect gas, which is widely used in high-voltage electrical equipment such as circuit breakers and high-voltage switchgear because of its excellent insulation performance and arc extinguishing ability. In recent years, the use and emission of SF₆ have been rising, and with the proposal of the dual carbon strategic goal, its harmless degradation has become an urgent problem to be solved. In this paper, SF₆ was degraded by pulsed DBD plasma technology and O₂. Studies have shown that the addition of O₂ can effectively promote the degradation of SF₆. With the increase in the added O₂ content, the DRE and EY of SF₆ first increased and then decreased. Under the conditions of the input power of 50 W, SF₆ concentration of 2%, and gas flow rate of 50 mL/min, the reaction system obtained the highest DRE and EY of 58.40% and 5.24 g/kWh when the O₂ content was 1%, respectively. In the SF₆/Ar/O₂/H₂O system, the addition of H₂O could improve the product selectivity of SO₂F₂, and when the O₂ concentration was 1%, the highest selectivity of SO₂F₂ was 48.96%, and the concentration was 8006.76 ppm. The addition of O₂ inhibited the production of SO₂, and with the addition of the O₂ system, SO₂F₂ and SOF₄ were the main components of degradation products; however, there were also SOF₂, SO₂, SiF_4, SF₄, etc. In this paper, the decomposition path of O₂ under SF₆ was analyzed in detail according to infrared spectroscopy and decomposition products. Full article

Direct barrier discharge (DBD) plasma is a potential antibacterial strategy for controlling Fusarium oxysporum (F. oxysporum) in the food industry. The aim of this study was to investigate the inhibitory effect and mechanism of action of DBD plasma on F. oxysporum. The result of the antibacterial effect curve shows that DBD plasma has a good inactivation effect on F. oxysporum. The DBD plasma treatment severely disrupted the cell membrane structure and resulted in the leakage of intracellular components. In addition, flow cytometry was used to observe intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential, and it was found that, after plasma treatment, intracellular ROS accumulation and mitochondrial damage were accompanied by a decrease in antioxidant enzyme activity. The results of free fatty acid metabolism indicate that the saturated fatty acid content increased and unsaturated fatty acid content decreased. Overall, the DBD plasma treatment led to the oxidation of unsaturated fatty acids, which altered the cell membrane fatty acid content, thereby inducing cell membrane damage. Meanwhile, DBD plasma-induced ROS penetrated the cell membrane and accumulated intracellularly, leading to the collapse of the antioxidant system and ultimately causing cell death. This study reveals the bactericidal effect and mechanism of the DBD treatment on F. oxysporum, which provides a possible strategy for the control of F. oxysporum. Full article

A new method of efficiently transforming water vapor into hydrogen was investigated by dielectric barrier discharge (DBD) loaded with bamboo carbon bed structured by fibrous material in an argon medium. Hydrogen productivity was measured in three different reactors: a non-loaded DBD (N-DBD), a bamboo carbon (BC) bed DBD (BC-DBD), and a quartz wool (QW)-loaded BC DBD (QC-DBD). The effects of the quality ratio of BC to QW and relative humidity on hydrogen productivity were also investigated in QC-DBD at various flow rates. The reaction process and mechanism were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy, N₂ physisorption experiments, infrared spectroscopy, and optical emission spectroscopy. A new reaction pathway was developed by loading BC into the fibrous structured material to activate the reaction molecules and capture the O-containing groups in the DBD reactor. A hydrogen productivity of 17.3 g/kWh was achieved at an applied voltage of 5 kV, flow rate of 4 L/min, and 100% relative humidity (RH) in the QC-DBD with a quality ratio of BC to QW of 3.0. Full article

Starch-based biodegradable films are a type of packaging material that can naturally decompose in the environment. Current challenges regarding starch-based film applications are their high solubility and low hydrophobicity. Prior studies have shown that plasma application improves the physical, chemical, and mechanical properties of these films. This work evaluates the plasma application strategy regarding the process stage in which plasma should be applied (starch granule, film-forming solution, or film). Three groups of films were produced: a film produced with the plasma-treated starch, a film produced by subjecting the film-forming solution to plasma treatment, and a plasma-treated film produced with the untreated starch. A 2² face-centered experimental design was applied to each group of films to attain the optimal film of each group. The design consisted of applying plasma at 100, 200, and 300 Hz for 0, 10, and 20 min to each group. The results showed significant differences regarding their physical-chemical and morphological properties. Most chemical changes occurred in the starch subjected to plasma prior to film formation, while the films produced with the untreated starch presented physical changes. Plasma-treated films presented reduced solubility and higher hydrophobicity. Full article

Non-thermal plasma (NTP) conversion applications have become an emerging technology of increasing global interest due to their particular ability to perform at atmospheric pressure and ambient temperature. This study focuses on a specific case of a dielectric barrier discharge NTP reactor for carbon dioxide conversion with the usage of argon as diluent gas. The plasma computations in COMSOL^® Multiphysics are compared to experimental results and coupled with previous thermodynamic characterization of argon species and fluid dynamic calculations. The model is defined as a time-dependent study with a 2D-Geometry of pure argon, with both fluid flow and plasma phenomena. Firstly, the model showcases an accurate understanding of the plasma physics involved, in the form of electron density, excited argon, argon ions, and mean electron energy. It also allows a direct comparison of the velocity, vorticity, pressure, and dynamic viscosity results with fluid flow computations. Secondly, the impact of several variables is studied, notably the inlet volumetric rate, dielectric barrier thickness and material, and reactor length. Limitations in the plasma characterization can occur by not including packed material or all relevant species in experimental CO₂ conversion and their respective reactions, which should be aimed at in future contributions. Full article

This perspective reports a process intensification strategy that converts methanol into ethylene glycol (MeOH-2-EG) in a single step to circumvent multi-step naphtha cracking into ethylene followed by ethylene epoxidation to ethylene oxide (EO) and the subsequent hydrolysis of EO to ethylene glycol (EG). Due to the thermodynamic restriction for the direct MeOH-2-EG, plasma-assisted catalysis was introduced, and platinum group metals were identified as prospective transition metal catalysts that can achieve the formation of strong metal hydride bonds and guarantee the controlled C–C coupling of two plasma-activated hydroxymethyl radicals (*CH₂OH) from methanol, both of which are essential for the single-step MeOH-2-EG. Full article