Search Results (150)

Glow-discharge plasma (GDP) poling is revisited as an electrode-free method for activating piezoelectricity in poly(vinylidene fluoride) (PVDF) films. Although this method was proposed several decades ago, its effect on the properties of PVDF films has remained poorly understood. In this work, we demonstrate that GDP enables efficient poling of oriented PVDF films without pre-deposited electrodes and investigate the relationship between plasma treatment time, structural evolution, and piezoelectric response. Commercially available 25 μm-thick oriented PVDF films (PolyK) were treated in a DC glow discharge for 15 s to 15 min and characterized using FTIR, DSC, piezoresponse force microscopy, UV–Vis–NIR spectrophotometry, quasi-static d₃₃ measurements and water contact-angle measurements. GDP poling produced a side-averaged piezoelectric coefficient d₃₃ of up to ~25 pC/N within 1–5 min, with local maxima at approximately 1, 2.5, and 5 min. This behavior was accompanied by pronounced changes in the domain structure, including an increase in the ferroelectric domain size from 86 to 552 nm, while the crystallinity and electroactive phase fraction changed only moderately. Plasma treatment also increased the wettability of the plasma-facing surface, reducing the water contact angle from about 85° to 42° within 3 min. At longer treatment times (>5 min), however, the piezoelectric response decreased and the optical transparency deteriorated because of increased haze and turbidity, most likely associated with plasma-induced chemical modification of the surface layers. These results indicate that GDP poling has an effective processing window of 1–5 min. The proposed approach provides a vacuum-compatible and electrode-free route for preparing PVDF films with increased surface wettability for flexible piezoelectric sensors, wearable electronics, and integrated polymer-based devices, because it is compatible with electrode deposition on an already activated polymer surface within a single vacuum cycle. Full article

This study presents a novel approach in millimeter wave (MMW) imaging by demonstrating the first experimental implementation of an imaging system that integrates optical up-conversion within a glow discharge detector (GDD) plasma alongside a phase-sensitive lock-in camera. In this novel approach, incident MMW radiation, modulated with an ON–OFF signal, strikes the GDD, which functions as an up-conversion sensor, transforming the MMW signal into ON–OFF-modulated near-infrared (NIR) optical emissions. This upconverted light is then captured by the lock-in camera, which synchronously demodulates the optical signal at each pixel. By simultaneously receiving the upconverted optical emissions and the original reference signal used to modulate the MMW radiation, the camera achieves synchronous demodulation of the incoming light at each pixel. This advanced configuration enables the direct extraction of amplitude and phase information with pixel-level synchronous demodulation, while actively and effectively increasing the SNR and eliminates the uncorrelated background plasma emissions. The proposed optical up-conversion system effectively addresses existing limitations, offering a unique combination of advantages. By inheriting the fundamental benefits of GDD, such as cost-efficiency per unit, simplified electronic design, and robust resistance to high radiation levels, the system demonstrates enhanced noise suppression and increased sensitivity. Validation experiments utilizing LED modulation verify an optical acquisition time of approximately 100 ms per scan position (pixel dwell time), representing a significant improvement of several orders of magnitude over conventional optical acquisition approaches. In the present proof-of-concept implementation, complete image formation additionally includes the mechanical scanning time required for image reconstruction. Ultimately, this work establishes an improved paradigm for MMW imaging, advancing the development of compact, rapid, and cost-effective imaging systems for advanced non-ionizing imaging applications. Full article

Hydrogen isotope retention in tungsten plasma-facing components affects particle recycling, plasma-density control, and tritium inventory management in fusion devices. In this study, a glow discharge cleaning (GDC) platform and a thermal desorption spectroscopy (TDS) system were used to investigate deuterium (D) retention in polished tungsten and the response of the retained D signal to He-GDC, H₂-GDC, and thermal baking treatments. Tungsten samples were first loaded by D₂-GDC and then characterized by TDS during programmed heating from room temperature to 917 °C at 10 K min⁻¹. Under the present data-reduction procedure, the D₂-GDC-only sample gave an apparent TDS-equivalent D inventory of approximately 7.85 × 10¹⁹ D m⁻², corresponding to about 29.5% of the estimated incident D fluence. Relative to this D₂-GDC reference sample, the normalized removal fractions were 9.3% for low-power He-GDC, 28.2% for high-power He-GDC, and 65.6% for the tested H₂-GDC condition. The H₂-GDC result is consistent with an isotope-exchange-assisted removal pathway, but the gas-species effect cannot be isolated because the H₂ and He treatments were not performed with identical pressure, duration, current, voltage, and sample-temperature histories. Stepwise baking at 240–350 °C did not fully suppress subsequent D-derived TDS release, indicating that part of the retained D remained in more stable trapping states. Because independent replicates and certified HD/D₂ sensitivity calibration were not available for all conditions, the inventories are reported as apparent values and the conclusions are restricted to normalized comparisons under the tested laboratory conditions. Full article

Expanding the operating pressure range of hollow cathode glow discharge to the region of 0.01–0.1 Pa makes it possible to use the discharge plasma in a number of technological processes that were previously not feasible, because pressure always exceeded p = 1 Pa. Implantation of nitrogen ions by means of application of 40 kV pulses to a steel workpiece immersed in plasma at p < 0.1 Pa allows production of a 40 µm thick surface layer with hardness of 13 GPa exceeding by 6.5 times the hardness of the bulk and a decrease in the processing time by an order of magnitude. Nitriding a steel workpiece at p = 0.1 Pa allows a substantial increase in the nitriding rate. The use of a titanium workpiece as a discharge anode with surface area not exceeding a critical value allows it to melt due to heating to the melting point of 1670 °C by electrons accelerated in the positive anode fall of potential. Full article

This study investigates the feasibility of obtaining high-temperature (2000–2200 °C) measurements using thermionic emission from a W–La₂O₃ cathode in a low-pressure argon glow discharge environment. Compared to a vacuum environment, the cathode emission characteristics and temperature variation patterns in a plasma environment exhibit significant differences. These differences arise primarily from the competitive interplay between the thermionic emission cooling (TEC) effect and the ion bombardment heating (IBH) effect. Among the discharge parameters (temperature, applied bias voltage, and background pressure), the applied bias voltage is the key factor influencing this competitive interplay. Consequently, the cathode surface temperature exhibits three distinct regions as a function of bias voltage: the TEC-dominated region (10–20 V), the transition region (20–40 V), where TEC and IBH are nearly in equilibrium, and the IBH-dominated region (40–60 V). The results indicate that by adjusting the discharge parameters to place thermionic emission in the transition region, the TEC and IBH effects can be mutually offset. Under these conditions, the cathode temperature can be unambiguously determined from the measured emission current using the modified Schottky equation. This approach simplifies the functional relationship between emission current and temperature (J–T), thereby enabling high-temperature measurements to be obtained. Full article

The effect of treatment time on arc-enhanced glow discharge plasma-assisted nitriding (AEGD-PAN) of AISI M2 high-speed steel was investigated for non-heat-treated and heat-treated substrates. Nitriding treatments were carried out at 350 °C for 1.5 and 3.5 h, producing diffusion layers with thicknesses ranging from approximately 38 to 75 µm without formation of a continuous brittle compound layer. X-ray diffraction combined with Rietveld refinement revealed the progressive formation of γ′-Fe₄N and ε-Fe₂₃N nitrides together with lattice expansion of the α-Fe matrix, indicating nitrogen supersaturation and precipitation strengthening within the diffusion zone. Heat-treated specimens exhibited higher surface hardness, reaching ~1350 HV_0.1, while non-heat-treated substrates developed pronounced hardness gradients associated with diffusion-controlled layer growth. Scratch testing showed improved resistance to contact-induced damage with increasing nitriding time, particularly for the 3.5 h treatment, where lateral cracking was significantly reduced and load-bearing capacity increased. Multi-pass scratch wear tests revealed a reduction in the Archard wear coefficient by up to four orders of magnitude compared with untreated M2 steel. These results demonstrate that AEGD-PAN at moderate temperature enables efficient diffusion layer formation and significant improvement in the tribological performance of high-alloy tool steels. Full article

Despite their significance as forensic targets, alkyl nitrites, classified as illegal drugs, have received little attention in forensic analysis due to their high volatility and chemical instability. Here, we present a high-performance analytical approach using a pulsed dc soft plasma ionization-quadrupole mass spectrometry (pulsed dc SPI-MS) system, uniquely designed to operate using ambient air as the discharge gas. In this system, the modulation of the duty ratio functions as a “structural probe” to identify reactive isomers. Unlike conventional dielectric barrier discharge (DBD) sources that typically operate at atmospheric pressure, our SPI system utilizes a controlled pressure regime of several kPa, where the nitrogen in the ambient air effectively functions as a third-body gas to suppress excessive internal energy. The control of the duty ratio in our pulsed dc SPI source allowed for the successful manipulation of ion–molecule reaction pathways for highly reactive analytes. By optimizing several parameters, including duty ratio and discharge pressure, we achieved a unique ionization regime where the molecular-related ion [2 M − 3 H]⁺ was predominantly detected as the base peak with minimal fragmentation. Notably, by reducing the duty ratio from 50% to 5%, both the target ion occupancy and signal intensity were significantly enhanced, achieving a limit of detection (LOD) as low as 0.16 parts per million by volume (ppmv). This sensitivity is several orders of magnitude higher than previously reported thresholds, enabling rapid identification of C4–C6 alkyl nitrite isomers. This method transforms the duty ratio into a powerful diagnostic tool for identifying reactive intermediates, providing a practical and efficient approach for the onsite identification of illegal alkyl nitrites in forensic and security fields. Full article

The present study investigates the effect of low-temperature ion plasma nitriding on the phase composition, microstructure, tribological behavior, and corrosion resistance of 30Cr13 martensitic stainless steel. Plasma nitriding was carried out at temperatures of 400, 450, and 480 °C in a dissociated ammonia atmosphere using a pulsed DC glow discharge. The phase composition and structural evolution of the surface layer were analyzed by X-ray diffraction, while the morphology and thickness of the modified zone were examined using scanning electron microscopy. The tribological properties were evaluated under dry sliding conditions using a ball-on-disk configuration, and corrosion resistance was assessed by potentiodynamic polarization in a 3.5 wt.% NaCl solution. It was established that low-temperature ion plasma nitriding leads to the formation of nitrogen supersaturated martensite (α′N) and the nitride phase ε-(Fe_2–3)N, with their relative fraction governed by the treatment temperature. An increase in the nitriding temperature resulted in a rise in the surface’s microhardness up to 1100–1150 HV and a change in the thickness of the modified layer, reflecting nitrogen redistribution between the solid solution and nitride constituents. The predominance of the α′N phase at 400–450 °C ensured the most stable tribological behavior and reduced corrosion rate, whereas an increased fraction of ε-(Fe_2–3)N at 480 °C led to a higher microhardness and a greater abrasive wear component while maintaining satisfactory corrosion resistance. The obtained results confirm the decisive role of phase composition in the nitrided layer in determining the tribological and corrosion performance of 30Cr13 steel, and may be used for optimizing the surface hardening parameters of components operating under combined friction and corrosive environments. Full article

Plasma nitriding is an advanced method to increase the hardness and wear resistance of different metal parts with complex shapes and geometries. The modelling is an appropriate approach for better understanding and improving such technologies based on multi-physical processes. Mathematical models of the coupled electromagnetic, fluid flow, and thermal processes in vacuum chambers for the low-temperature plasma treatment of metal parts have been developed. They were solved numerically via ANSYS/CFX software for a discretized solid and gas space of a plasma nitriding chamber. The specific electrical conductivity of the gas mixture, containing plasma, has been calibrated on the basis of an electrical model of the chamber and in situ measurements. The three-dimensional fields of pressure, temperature, velocity, turbulent characteristics, electric current density, and voltage in the chamber have been simulated and analysed. Methods for further development and application of the models and for technological and constructive enhancement of the plasma treatment technologies are discussed. Full article

The persistence of organochlorine pesticides, such as Aldrin and Dieldrin, in water bodies worldwide necessitates the development of efficient Advanced Oxidation Processes (AOPs) for water treatment or remediation. However, comparative studies evaluating the performance of distinct plasma discharge geometries against acoustic cavitation for the mineralization of these specific chlorinated cyclodienes remain scarce. This study investigates the comparative efficacy of four non-thermal technologies, ultrasound, dielectric barrier discharge (DBD) plasma, glow discharge plasma, and corona discharge plasma, for the simultaneous degradation of Aldrin and Dieldrin in a model contaminated aqueous solution (5 μg/L). All experiments followed a 3²-factorial design, and the residual concentrations of these pesticides were quantified by GC-MS after Solid-Phase Microextraction (SPME). All four methods achieved high degradation efficiencies, ranging from 92.5% to 100% for Aldrin and 92.6% to 99.2% for Dieldrin. Corona discharge plasma achieved the highest performance, resulting in 100% removal of Aldrin. However, ultrasound proved to be the most advantageous, achieving a 98% removal efficiency for both pesticides under its mildest conditions (3125 W/L ultrasonic power density for 3 min). The study confirmed that while Aldrin is highly susceptible to these technologies, Dieldrin remains the limiting factor for regulatory compliance. Chemical analysis did not conclusively identify any organic degradation by-products, suggesting that these AOPs may promote complete mineralization of the pollutants. Full article

The synthesis of nanoparticles in the plasma of a stratified DC gas discharge was carried out under typical gas discharge conditions, i.e., at room temperature and an argon pressure of 0.11 torr, with a discharge current of 2.5 mA. The particles were formed and grown due to the sputtering of a dielectric plasma concentrator, which was used for strata stabilization. The analysis of the material collected using double-sided carbon tape placed on the glass wall of the discharge tube was performed by scanning electron microscopy and X-ray energy-dispersive microanalysis after the experiments. Three distinctive groups of particles of different shape and size were found, i.e., smooth spherical nanoparticles with a size of 10–100 nm, the main group of smooth spherical and dumbbell-like particles with a size of 200–500 nm, and micron-sized particles of complex cauliflower-like shape. EDX microanalysis of the synthesized nanoparticles revealed that the particles mainly consist of C, O, and Si, which proves that they were formed from the sputtered material of the silicone dielectric concentrator. Analysis of the particles and plasma parameters was performed, and a probable mechanism for the formation of such particles is proposed. Full article

This study systematically investigates the effect of hydrogen flow rate (100, 200, 300, and 400 sccm) on the properties of DC53 steel during a 4 h plasma nitriding process conducted at 400 °C in an asymmetric bipolar pulsed reactor. A comprehensive characterisation approach was employed. X-ray diffraction (XRD) was used to identify the phase composition, revealing the formation of a compound layer consisting of ε-Fe_2–3N (identified by its (100), (101), and (102) planes) and γ’-Fe₄N (identified by its (220) plane). Mechanical properties were assessed using Vickers microhardness for surface measurements and nanoindentation for depth profiling. Glow discharge optical emission spectroscopy (GD-OES) provided elemental depth analysis, while a ball-on-disk tribometer evaluated the tribological performance. The optimal treatment was achieved at a hydrogen flow rate of 200 sccm. This condition yielded a peak surface hardness of 1121.5 ± 69.2 HV_0.2. GD-OES analysis directly correlated this mechanical enhancement to a high surface nitrogen content of approximately 8.5% and an effective diffusion depth of about 50 µm. Full article

The deposition characteristics of coatings on a titanium alloy substrate were compared using two alternative surface preparation methods: Hollow Cathode Spaces (HCSs) and Ion Bombardment (IB). After deposition of ZrN coatings, the wear resistance of the samples increased by 50–70% compared to uncoated samples, while the HCS method provided 30% higher wear resistance than the IB method. Coated samples deposited using the HCS and IB methods demonstrated very similar friction coefficient values, with a slight (10–15%) decrease in this parameter for the HCS samples. Varying the bias voltage on the substrate (−900, −1200, and −1500 V) when using the HCS method significantly affected wear resistance. The calculated optimal value of the bias voltage when using the HCS method is −1126 V. During the pre-treatment of the substrate using the HCS and IB methods, a transition layer can be formed in the area of the coating–substrate interface; the thickness of this layer varies within the range of 15–400 nm, and the composition is a mixture of coating (zirconium) and substrate (titanium, aluminum, and vanadium) materials. Full article

This paper addresses the formation of nitrided layers on CP Titanium Grade 2 substrates under direct current (DC) glow discharge conditions. In the preliminary research, the parameters for glow discharge plasma nitriding were selected, and the threshold process temperature was determined to ensure the formation of a continuous and uniform titanium nitride layer on the nitrided samples using the active screen method. On the other hand, the core research involved further detailed analysis of the formed surface layers at nitriding temperatures of 685 °C, 700 °C and 715 °C. It has been demonstrated that the nitriding of CP Titanium Grade 2 under DC glow discharge conditions using an active screen enables the formation of surface layers with uniform thicknesses and proper structures over the entire surface of the nitrided component. Full article

The application of plasma technology in agriculture has emerged as a promising approach to enhance plant health and manage microbial interactions, offering potential solutions for sustainable crop production and disease control. This study contributes to this field by exploring the effects of plasma treatments on plant physiology and microbial dynamics, with a focus on their potential to improve agricultural outcomes. This investigation aims to systematically determine optimal plasma seed treatment parameters for enhancing plant vigor and promoting beneficial microbial associations while minimizing pathogenic interactions in Arabidopsis thaliana. This study focuses on understanding the effects of various plasma treatments on chlorophyll content, root length, microbial growth, and microbial quantification in plants and microbes. The treatments involve the use of an atmospheric jet plasma handheld device, a globe plasma, and a glow discharge plasma chamber with air and argon. These treatments were applied for varying time durations from 10 s to 5 min. The results demonstrated that the globe plasma treatment for 1 min significantly enhanced chlorophyll a extraction and root length, outperforming the other treatments. Additionally, the study examined the impact of plasma on plant–microbe interactions to assess whether plasma treatments affect beneficial microbes. Plasma treatments showed minimal impact on most beneficial microbe activity, though species-specific sensitivities were observed, with Pseudomonas cedrina showing moderate growth inhibition, revealing no significant disruption to their activity. The microbial quantification assays indicated that the globe plasma treatment effectively reduced microbial counts, while combined treatment with plant and microbe plasma together did not yield significant changes. Additionally, the chlorophyll estimation of plasma-treated samples indicated that the globe plasma and atmospheric jet plasma treatments were effective in enhancing chlorophyll content, whereas the combined treatment with both plant and microbe plasma did not yield significant changes. These findings suggest that plasma treatments, especially the globe plasma, are effective in improving plant health and controlling microbial activity. Future research should focus on optimizing plasma conditions, exploring the influence of plasma parameters and the underlying mechanisms, and expanding the scope to include a wider range of plant species and microbial strains to maximize the benefits of plasma technology in agriculture. Full article