Air Plasma Research Articles

Isotactic-polypropylene (iPP) wettability modified by surface DBD plasma

In this paper, atmospheric pressure plasma of ambient air was generated by a surface dielectric barrier discharge (SDBD) device for the purpose of modifying the surface of isotactic-polypropylene (iPP). The effect of SDBD treatment time on the chemical and physical properties of iPP was studied using various analytical techniques including, water contact angle (WCA), attenuated total reflection (ATR), Raman spectroscopy, x-ray diffraction (XRD), and atomic force microscopy (AFM). The results indicate that the hydrophilicity and the C=O bonds of the treated iPP were improved as observed, respectively, through WCA and ATR analysis. The crystal structure was evaluated by Raman spectroscopy and XRD. It was found that the iPP chain was under microscopic stress, which affected its crystallinity degree depending on the duration of the treatment. Furthermore, the AFM analysis revealed that the surface roughness was substantially modified.

Surface activation of viscose textiles via air, argon, and oxygen dielectric barrier discharge plasma: influence of peak voltage

This paper discusses the use of atmospheric pressure dielectric barrier discharge (DBD) plasma treatment to enhance the surface qualities of viscose fabrics. The study explores the effects of different plasma gases, discharge voltages, and exposure times on the treated fabrics. The findings emphasize the importance of optimizing the plasma’s peak voltage to achieve the desired surface treatment outcomes. The document also presents data on colour strength, wettability, colour fastness, and tensile strength of the treated fabrics, as well as scanning electron microscopy (SEM) analysis of surface morphology and chemical analysis using fourier- transition infrared spectroscopy (FTIR) and energy dispersive X-ray (EDX). The results show that treatment at a peak voltage of 11.83 kV is more efficient, except for the tensile strength which is enhanced at a peak voltage of 8.92 kV. The oxygen plasma treatment significantly improves the colour strength, which exhibits an increase from 11 to 18. The intensified colour was attributed to the significant influence of electrostatic interactions between the charged hydroxyl groups of the oxygen plasma treated viscose textiles and the dye molecules, which enhance the printability. The oxygen DBD plasma exhibits a higher ability to enhance the properties of textiles when compared to air and argon plasmas. This study presents a sustainable, economical, secure, and ecologically friendly approach to explore new fabrics for specific uses.

Air Plasma Modification of Graphite-Based Electrode for Improved Performance of Aqueous Redox Flow Batteries

Graphite felt is widely utilized as a porous carbon electrode in aqueous redox flow batteries (RFBs). However, its inherent hydrophobic nature and limited electrochemical activity present challenges. While the correlation between RFB performance and electrode properties has been extensively studied for vanadium chemistry and other inorganic redox active materials, it remains scarce in literature for organic systems. In this study, we employ air plasma treatment, known for its controllability, solvent-free nature, and short treatment duration, to modify commercially available graphite felt for RFB applications. A comprehensive analysis is conducted to establish correlations between plasma treatment, physical properties, electrochemical characteristics, and overall cell performance in aqueous RFBs. Comparative evaluation reveals a significant enhancement, with treated graphite felt exhibiting an 85% increase in capacity at 140 mA cm−2 compared to its pristine counterpart. By intentionally utilizing authentic RFB electrodes and employing state-of-the-art ferrocyanide posolyte, this study underscores the crucial role of the interface, even for rapid (reversible) redox-active materials utilized in AORFBs.

Plasma sprayed duplex ytterbium disilicate/monosilicate EBCs and the transformation from ytterbia to ytterbium monosilicate during burner rig testing

Environmental Barrier Coating systems (EBCs) were thermally cycled in a burner rig test facility. Yb2Si2O7 (YbDS) layer was deposited by air plasma spraying while two suspension plasma sprayed Yb2SiO5 (YbMS) microstructures were evaluated in duplex (YbDS/YbMS) systems: columnar and segmentation cracked. EBCs underwent 2000 cycles at a surface temperature of 1300 °C without signs of delamination failure. A porous YbMS layer formed at the base of intercolumnar gaps and segmentation cracks in the duplex systems, presumably due to reactions with entrapped water vapor. Furthermore, Yb2O3 depletion zones were evident at both the surface and YbDS/YbMS interface of the duplex EBCs.

Silicon (100) surface passivation-driven tuning of Ag film crystallinity and its impact on the performance of Ag/n-Si mid-infrared Schottky photodetector

The utilization of metal/semiconductor Schottky devices for plasmonic harvesting of hot carriers holds immense potential in the field of sub-bandgap photodetection. In this work, we explore a surface passivation scheme using air plasma exposure to modify the Si (100) surface and subsequently the crystal orientation of the deposited Ag film for photon detection in the mid-infrared (MIR) regime. This tailoring was achieved by varying the plasma exposure duration (0, 150, 300, 450, and 600 s). As a result, we could tune the crystal orientation of Ag from the (200) to the (210) crystal plane, with the Ag (111) orientation present in all devices. Furthermore, the photo-response behavior under MIR exposure at λ = 4.2 µm was studied both experimentally and using COMSOL simulations. It was observed that both photoelectric (PE) and photothermal (PT) effects contributed to the photo-response behavior of all devices. The Ag/Si device exposed to air plasma for 300 s exhibited the maximum PE-driven response (2.73 µA/W), while the device exposed to air plasma for 600 s showed a significant PT-driven response (13.01 µA/W). In addition, this strategy helped reduce the reverse leakage current by up to 99.5%. This study demonstrates that MIR detection at longer wavelengths can be optimized by tailoring the crystal orientation of the metal film.

Effect of pre-plasma on terahertz radiation from two-color laser plasma filaments in a collinear geometry.

Terahertz (THz) radiation from air plasma in the presence of pre-plasma in a collinear geometry is investigated experimentally, where the pre-plasma is formed by a pre-pulse with a Gaussian beam profile and the measured THz radiation is driven by a main laser pulse. The pre-plasma has a de-focusing effect for the main pulse passing through it, which reduces the effective length of the plasma filament formed by the main laser pulse for THz radiation. It is found that only the part not overlapped by the pre-plasma can actually produce THz radiation. Thus, the amplitude of the THz pulse driven by the main pulse can be modified by changing the spatial separation between two plasma filaments. The experimental observations are qualitatively in agreement with our numerical simulation results. It is also found that the change of the time delay between the pre-pulse and the main pulse does not change the THz radiation amplitude for a given spatial separation. This study suggests a practical way for the manipulation of THz waves through an interaction between laser plasma filaments.

Comparative Study on the Microstructure and Properties of 304 Stainless Steel Coatings Prepared by High-Velocity Oxygen Fuel Spraying and Air Plasma Spraying

Comparative Study on the Microstructure and Properties of 304 Stainless Steel Coatings Prepared by High-Velocity Oxygen Fuel Spraying and Air Plasma Spraying

Renewable cold plasma exposed activated carbon-derived eucalyptus leaves (EL) as electrode in fabricating low-cost energy storage devices

ABSTRACT The activated carbon made from Eucalyptus leaves was created using an environmentally friendly physical activation process, and it was then subjected with the low temperature plasma to increase its surface area and porosity, as shown by structural and morphological characteristics. The nanoparticles’ surface layers are altered by the plasma treatment, improving surface characteristics like wettability, adhesion, and surface area that were investigated using structural, morphological, and electrochemical studies. The air-plasma-treated KOH exhibits a specific capacitance of 1591 F/g for 1.5 mA, which can be utilized to prepare an electrode material for the energy storage application. The electrochemical investigation was conducted for the untreated and air, oxygen-plasma-treated carbon, demonstrating the better specific capacitance for the air plasma treatment, which can be used to prepare an electrode material for the low-cost fabrication of the devices.

Wear and corrosion properties of laser treated Cr2O3 on stainless steel

In this study, a highly wear and corrosion resistance coating was fabricated on 304 stainless steel. Herein, air plasma spray coating of Cr2O3 was deposited on 304SS which was subsequently treated with laser at different travel speeds these were: 25 mm/min, 50 mm/min and 100 mm/min, respectively. The morphology of coatings was studied by using scanning electron microscopy. It revealed that ultrafine grain structure is found as travel speed is increased, the as-solidified microstructure got more and more refined. Wear test demonstrated that with increase in laser t speed, the wear rate increaased. Furthermore, wear rate of laser treated coating at travel speed of 25 mm/min exhibits very comparable result at 8 N and 16 N. The potentiodynamic polarization results described that pitting potential was increased and current density (Icorr) was decreased two orders of magnitude for laser treated coating at travel speed of 25 mm/min as compared to faster laser scan rate

Two-dimensional temperature measurements in laser-induced air plasma

Two-dimensional temperature measurements in laser-induced air plasma

Outstanding specific capacitance of air plasma exposed MgCoSiO4 cathode in the rechargeable magnesium batteries

Outstanding specific capacitance of air plasma exposed MgCoSiO4 cathode in the rechargeable magnesium batteries

Sustainable Plasma Gasification Treatment of Plastic Waste: Evaluating Environmental, Economic, and Strategic Dimensions.

The conversion of waste to energy is an essential process in the Middle East, especially in Saudi Arabia, where it plays a crucial role in waste management. The annual analysis of the decomposition hazards of the landfills in the city of Makkah showed that they ranged from 168,000 Mg in 1994 to 297,000 Mg in 2022. The emission costs of pollution ranged from 4 million in 1994 to 7 million in 2022. The number of gas emissions of plastic waste accumulating in the analyzed landfill has increased from 128,000 Mg in 1994 to 227,000 Mg in 2022. The thermal plasmas used were produced by air plasma torches, which are an essential part of plasma reactors. The operational characteristics of air plasma torches were investigated at a flow rate of 10-30 g/s, including current-voltage characteristics, applied power, applied flow rate, average temperatures of the exiting plasma jet ranging from 15,000 to 19,000 K, average velocity of the exiting plasma jet (1677.3-2763.2) m/s, wavelength of the emitted radiation ranging from 153 to 193 nm, and the corresponding beam lengths ranging from 400 to 450 mm. The proposed plasma gasification is the greenest method for processing plastic waste in the light of ecological, economic, and strategic visions with an amount of recovered pyrolysis oil in the year 2022 of 3.17 × 105 tons with an equivalent energy of 12.55 × 109 MJ, with an output efficiency value equal to 81%. A roadmap for the economic and environmental visions was introduced, where the economic return on investment (ROR%) was 80%, the payback period (PBP) was 1.2 years, and the gross profit reached 129%.

Effect of Cold Plasma Seed Treatment on Physiological and Biochemical Changes in Aged Mustard Seed Variety-RH0749

The low rate of seed germination is a major problem in modern agriculture. Cold-activated air plasma has been tested as a pre-treatment method to improve the rate and uniformity of the germination. In view of the widespread cultivation of mustard in India and other parts of the world, This study was conducted to determine alternative non-destructive seed treatment method based on cold plasma chemistry would offer a more viable alternative over traditional seed coating technologies Seed physiological characteristics as was modified in aged low vigour mustard seeds by coating the surface of the seeds with cold plasma process using a rotating plasma reactor during 2023-24 at CCS HAU, College of Agriculture Bawal. The source of atmospheric oxygen gas, nitrogen and heliun gas entering the plasma chamber during the reaction process determined the type of coating. Among the different treatments imposed, seed treatment with 300V at 10 Min significantly enhanced seed quality attributes viz., germination ( 92 %), root length ( 4.37 cm), shoot length ( 6.98 cm), mean seedling length (11.0 cm ), Seedling dry weight (2.67 mg) and SVI-I (1115), SVI-II (254), TDH (0.78 A480 nm) with lower electrical conductivity (14.20 dsm-1). The inhibitory effect noticed with a higher dose of plasma of 400v at 10 min suggested the need for judicious usage of these plasma frequencies in such applications. The first-ever report on the effect of new plasma state on seed germination and establishment of mustard revealed the positive influence that could be used as a seed treatment to enhance seed yield and quality.

Study of the synthetic silica functionalization effect on wettability of oxidized polypropylene film by plasma discharge

AbstractThis work describes the effect of functionalized silica, treated with organosilane (γ‐methacryloxypropyltrimethoxysilane), on the wettability loss of polypropylene (PP) film when exposed to surface oxidization treatment by atmospheric air plasma. The observed wettability loss results from the spontaneous process within the polymer matrix, which reduces surface energy, causing oxidized polymer molecules to move toward the bulk of the film. The effect of silica's functionalization on the initial wettability of oxidized PP film and its loss on storage time is measured by contact angle. Elemental analysis of the modified silica, employing acid catalytic processes, reveals the highest functionalization yield. Silicon nuclear magnetic resonance shows that the post‐condensation process negatively affects structures formed by the organosilane, eliminating three‐dimensional bonds and reverting it to its original and hydrolyzed state. The solvent extraction process and elemental analysis confirm that the concentration of organosilane in the chemically bonded layer, which was around 9 wt%, is not influenced by the post‐condensation treatment. Notably, silica functionalized with the highest concentration of organosilane has significantly improved initial wettability when oxidative treatment occurs within a shorter residence time (30 s), which achieved a contact angle of 53.8° against 59.1° for the film with untreated silica. However, the wettability loss rate of the materials remains unaffected by the presence of functionalized silica.

Visualization of electrical interaction among close-packed atmospheric pressure plasma jets

Plasma jet arrays can flexibly generate large-scale plasma in ambient air for surface treatment. Close arrangement of plasma jets inevitably induces a complex electrical interaction, which reshapes plasma plumes and destabilizes the treatment process. Understanding electrical interaction is a prerequisite for optimizing parameters in surface treatment. In this study, we employ a linear electro-optic technique to visualize the electrical interaction on the cross section perpendicular to plume trajectories. The strength of the interaction is featured by the density of the deposited surface charge. Results show that plasma jet arrays can simultaneously deposit like-charged groups onto the substrate. However, the electrical interaction is proven to behave with a tendency toward convergence rather than the repulsion caused by electrostatic interaction. It is inferred that electrons at the head of ionization waves (IWs) shield electrostatic repellence between positive charge groups. The collision ionization by electrons in the interval guides the coalescence of adjacent IWs. This study clarifies the electrical interaction between multiple jets, which is instructive for stable control of large-scale non-thermal plasmas for surface treatment.

Cold Air Plasma Inhibiting Tumor-Like Biological Behavior of Rheumatoid Arthritis Fibroblast-Like Synovial Cells via G2/M Cell Cycle Arrest.

Rheumatoid arthritis fibroblast-like synovial cells (RA-FLS) have become the core effector cells for the progression of rheumatoid arthritis due to their "tumor-like cell" characteristics, such as being able to break free from growth restrictions caused by contact inhibition, promoting angiogenesis, invading surrounding tissues, and leading to uncontrolled synovial growth. In recent years, cold air plasma (CAP) has been widely recognized for its clear anticancer effect. Inspired by this, this study investigated the inhibitory effect of CAP on the tumor-like biological behavior of RA-FLS through in vitro experiments. Treatment of RA-FLS with CAP at different time doses (0s, 30s, 60s, 120s). 5-ethynyl-2'-deoxyuridine (EdU) proliferation assay was used to determine the cell viability. Analysis of cell migration and invasion was performed by wound-healing assay, transwell assay and immunofluorescent staining for f-actin, respectively. Flow cytometry technique was used for analysis of cell cycle and determination of reactive oxygen species (ROS). Hoechst staining was used for analysis of cell apoptosis. Protein expression was analyzed by Western blot analysis. Molecular and cellular level mechanisms have revealed that CAP blocks RA-FLS in the G2/M phase by increasing intracellular reactive oxygen species (ROS), leading to increased apoptosis and significantly reduced migration and invasion ability of RA-FLS. Overall, CAP has significant anti proliferative, migratory, and invasive effects on RA-FLS. This study reveals a new targeted treatment strategy for RA.

Evaluation of degradation efficacy and toxicity mitigation for 4-nitrophenol using argon and air-mixed argon plasma jets

This paper investigates the effects of argon (Ar) and that of Ar mixed with ambient air (Ar–Air) cold plasma jets (CPJs) on 4-nitrophenol (4-NP) degradation using low input power. The introduction of ambient air into the Ar-Air plasma jet enhances ionization-driven processes during high-voltage discharge by utilizing nitrogen and oxygen molecules from ambient air, resulting in increased reactive oxygen and nitrogen species (RONS) production, which synergistically interacts with argon. This substantial generation of RONS establishes Ar–Air plasma jet as an effective method for treating 4-NP contamination in deionized water (DW). Notably, the Ar-Air plasma jet treatment outperforms that of the Ar jet. It achieves a higher degradation rate of 97.2% and a maximum energy efficiency of 57.3 gkW−1h−1, following a 6-min (min) treatment with 100 mgL−1 4-NP in DW. In contrast, Ar jet treatment yielded a lower degradation rate and an energy efficiency of 75.6% and 47.8 gkW−1h−1, respectively, under identical conditions. Furthermore, the first-order rate coefficient for 4-NP degradation was measured at 0.23 min−1 for the Ar plasma jet and significantly higher at 0.56 min−1 for the Ar–Air plasma jet. Reactive oxygen species, such as hydroxyl radical and ozone, along with energy from excited species and plasma-generated electron transfers, are responsible for CPJ-assisted 4-NP breakdown. In summary, this study examines RONS production from Ar and Ar–Air plasma jets, evaluates their 4-NP removal efficacy, and investigates the biocompatibility of 4-NP that has been degraded after plasma treatment.

Selective Cu electroplating enabled by surface patterning and enhanced conductivity of carbon fiber reinforced polymers upon air plasma etching

We demonstrate a sustainable post-processing of carbon fiber reinforced epoxy polymer (CFRP) composites by air plasma etching that permits regular electroconductive surface patterning through direct Cu galvanic metallization, in contrast to the untreated composite. Our study reveals a significant property dependence of the composite with respect to the position to the fiber/matrix composite surface and treatment. The enhancement in electrical conductivity was not compromised by the lower structural integrity of the composite, as the embedded carbon fibers remained unaffected by the air plasma etching process. The metallized Cu domains on the composite exhibit good hardness and excellent solderability potential. Thus, the electroconductive surface patterning of the composite, preceding galvanic metallization, facilitates the selective deposition of Cu layer domains. This step by step process, relying on the creation of selective electroconductive areas on the composite by plasma etching, enables galvanic metallization. Consequently, it enhances the potential for multifunctional composite applications. The feasibility of galvanic metallization brings new perspectives in selective metallization of composites by allowing the tailoring of the metal layer thickness, microstructure and selection of the metal.

An opportunity for post‐harvest seafood safety: atmospheric pressure air or helium cold plasma to control Salmonella Enteritidis in sea bass

SummarySalmonella contamination of fish after harvest is a significant food safety risk. To control this risk, it was aimed to reduce Salmonella Enteritidis in sea bass by helium and air plasma. Considering that preserving the fresh properties of sea bass is important for industrial applicability, determining the sensory effects of plasma treatments was also aimed. Since air plasma would provide a cheaper and easier alternative to helium plasma, their effects were compared. Additionally, the in vitro effects of these treatments on Salmonella Enteritidis were also investigated. Air and helium plasma completely inhibited the initial load of S. Enteritidis (2.79 Log CFU) inoculated on agar surface after 10 min treatment. Then, the inoculated sea bass samples were exposed to air or helium plasma for durations ranging from 1 to 15 min. Air and helium plasma treatments for 10 min provided 0.90 log cfu g−1 and 1.13 Log CFU/g reductions, respectively, but longer treatments did not lead to further significant reductions. Sensory scores were all above 7 (good) when samples were treated with air or helium plasma for 1–10 min, but longer treatments resulted in lower scores. The reduction of S. Enteritidis and changes in sensory characteristics were interpreted together and it was concluded that 10 min of air or helium plasma provided maximum reduction without causing any significant sensory changes. Overall, the current study showed that atmospheric pressure air and helium plasmas can be useful for ensuring post‐harvest safety in the fish trade.

Excitation of optically trapped single particles using femtosecond pulses.

Excitation from optically trapped particles is examined through laser-induced breakdown spectroscopy following interactions with mJ-level fs pulses. Optical emissions from sub-ng ablation of precisely positioned cupric oxide microparticles are used as a method to spatially resolve laser-particle interactions resulting in excitation. External focusing lenses are often used to change the dynamics of nonlinear self-focusing of fs pulses to form laser filaments or, alternatively, to form very intense air plasmas. Given the significant implications external focusing has on laser propagation and plasma conditions, single-particle emissions are studied with focusing lenses ranging from 50 to 300 mm. It is shown that, while single particles are less excited at longer focal lengths due to limited energy transfer through laser-particle interactions, the cooler plasma results in a lower thermal background to reveal resolved single-shot emission peaks. By developing an understanding in the fundamental interaction that occurs between single particles and fs pulses and filaments, practical improvements can be made for atmospheric remote sensing of low-concentration aerosols.