Low-pressure Glow Discharge Plasma Research Articles

Dyeing jute-cotton blended fabric with natural dyes: A chemical-free approach of LPGD plasma technology using O2 and N2 gases

In response to growing environmental concerns in the textile industry, this study investigates the effects of a low-pressure glow discharge (LPGD) plasma with oxygen (O2) and nitrogen (N2) gases on the dyeing process of jute-cotton (JC) blended fabrics, using coffee extract as a natural dye source. The hydrophilic properties of all the JC blended fabric samples were enhanced due to plasma treatments. The contact angles of the samples were significantly decreased from 131° to 52° (O2) and 55° (N2) after 20 minutes of plasma treatment. Compositional analysis revealed new functional groups e.g., CO and N−H, on the fabric's surface after plasma treatment. Surface morphology analysis indicated that the surface roughness of the treated fabric was increased with plasma treatment time. The improvement of the wicking properties of the fabric with contact time was also observed. All the plasma-treated fabric samples exhibited good colour strength (k/s), wash fastness, and rubbing fastness. After plasma treatment with O2 gas for 20 minutes, the k/s value had increased from 3.6 to 4.9. Washing and rubbing (dry) color fasting ratings were enhanced from 1 to 3 and 2–4, respectively, following a 20-minute plasma treatment with O2 gas. Although both O2 and N2 plasma treatment showed a significant impact on the dyeing properties of JC blended fabric, O2 gas provided better results compared to N2 gas plasma treatment.

Protein ion yield enhancement in matrix-assisted laser desorption/ionization mass spectrometry after sample and matrix low-pressure glow discharge plasma irradiation.

Plasma-assisted ionization is widely used in mass spectrometry; in this study, a low-pressure glow discharge is introduced as a new method to improve the detection of large proteins, and bovine serum albumin (BSA) is used as a protein model. The treatment of analyte, matrix, and the matrix/analyte mixture is evaluated under optimal conditions. Low-pressure radio-frequency capacitively coupled plasma (RF-CCP) treatment is utilized in the sample preparation step of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to enhance the protein MALDI ion signal. Plasma treatment can be an effective tool for enhancing the non-covalent binding of the analyte with the matrix, incorporation of the analyte into the matrix, production of matrix/analyte crystals, and analyte protonation through plasma activation, resulting in an improved MALDI ion signal. Fourier-transform infrared (FTIR) spectroscopy allows us to distinguish between the functional groups of plasma-treated and control samples. In addition, optical emission spectroscopy (OES) determines the plasma species, and zeta potential analysis characterizes the potential difference between plasma-treated and control samples before MALDI-TOF MS analysis. Plasma-treated BSA can provide a five-times enhancement of ion intensity. The combination of the plasma-treated analyte with the plasma-treated matrix leads to an increase in the ion intensity by a factor of 14. Low-pressure glow discharge plasma treatment greatly enhances MALDI ion signals, with a noticeable increase in incorporation, co-crystallization, protonation, and the concentration of the sample functional groups.

Aluminum: An underappreciated anode material for lithium-ion batteries

Aluminum has excellent intrinsic properties as an anode material for lithium ion batteries, while this application is significantly underappreciated. Due to the high chemical reactivity of Al, bottom-up preparation of Al nanostructures is very challenging and Al based anode with high capacity and good stability is extremely challenging. In this work, we developed a plasma method to address the synthetic challenge. Using AlCl3-H2-CH4 plasma with the addition of low amount of FeCl3, a homogeneous Al-Fe/C nanocomposite with uniform particle size around 40 nm is obtained at near room temperature. The low pressure glow discharge plasma generates highly reactive intermediates such as AlCl and H radicals, which allows direct reduction of AlCl3 to metal Al in mild conditions. The plasma enabled reaction leads to performance breakthrough of the Al based anode materials, which suggests that Al should be more seriously considered as a promising candidate anode material for LIBs.

Surface Hardening of Massive Steel Products in the Low-pressure Glow Discharge Plasma

A process vacuum chamber is filled with a homogeneous plasma of glow discharge with electrostatic electron confinement, which is used for surface hardening of massive products. At the current of 2–20 A and the gas pressure ranging from 0.1 to 1 Pa the discharge voltage amounts to 350–500 V. When a bias voltage of 2 kV is applied to an immersed in the plasma hollow cylinder with a mass of 15 kg, electrical power spent on heating it by accelerated ions exceeds by an order of magnitude the power spent on the discharge maintenance. The massive cylinder is heated up to 700 °C for 15 min. When argon mixture with nitrogen (30%) is used, the nitriding for 3h results in an increase in the surface hardness from 400 up to 1000 HV50 and the nitrided layer thickness grows to ~100 μm. The nitriding rate is enhanced by a high degree of nitrogen dissociation due to decomposition by fast electrons and surface structural defects due to bombardment by high-energy ions.

Optical and electrical properties of plasma surface treated polymethylmethacrylate films

Abstract In the present study, the optical and electrical properties of Polymethylmethacrylate (PMMA) films have been investigated under the effect of direct current (DC) glow discharge plasma. PMMA films have been prepared and treated with low-pressure DC glow discharge plasma at different plasma conditions; mainly various working gas and plasma treatment time. The optical and electrical properties of the treated PMMA samples were measured and compared to the untreated one. Nitrogen, argon, and nitrogen-argon mixture have been used as working gases. Plasma parameters, such as the electron density, the ion density, and electron temperature, were measured, at the position of the PMMA films, using Langmuir probe. The results reveal that, the optical properties of PMMA were found to be more sensitive to N2- plasma treatment than Ar and N2-Ar gas mixture. The optical energy gap showed a decreasing behavior with increasing the treatment time of N2 plasma however, the band tail width and the electrical resistivity increased.

Strengthening of cutting tools using beams of fast neutral atoms in a low-pressure gas discharge plasma

The surface of a 26-mm-diameter reamer made of AISI M2 high-speed steel has been nitrided in a low-pressure glow discharge plasma. Then a 3-μm-thick wear-resistant TiN coating has been magnetron sputtered on the hardened surface. After the combined processing the reamer’s cutting edges radii grew from the initial value of ∼8 μm up to ∼37 μm. The reason for the strengthened tool blunting is selective sputtering of the edges by heating ions accelerated from the plasma. Another reamer under nitriding was heated by a beam of fast atoms arriving at the tool surface from an immersed in the plasma concave grid negatively biased to 6 kV. Due to the uniform sputtering of the tool surface by the beam, the edges radii after nitriding and 3-μm-thick TiN coating deposition did not exceed the initial value.

Operando FT-IR study on basicity improvement of Ni(Mg, Al)O hydrotalcite-derived catalysts promoted by glow plasma discharge

CO2 adsorption on the surface of hydrotalcite-derived mixed oxide catalysts was investigated under low pressure glow discharge plasma in operando conditions via FT-IR spectroscopy. Nickel catalysts were promoted with various transition metal species (Ce, Fe, La, Zr) to influence their physico-chemical properties. Fe and Zr species were successfully incorporated into hydrotalcite brucite layers. After calcination formed a single phase with Ni(Mg, Al)O mixed oxide, while La and Ce species formed separate phases. This had a consequence in the distribution of surface basic sites as well as in the affinity to CO produced upon CO2 dissociation in plasma. Plasma treatment activated the surface of prepared materials and changed their properties via the generation of strong basic sites associated with low coordinated surface oxygen anions. Moreover, the CO2 adsorption capacity of prepared materials increased after plasma treatment.

Effect of Radiofrequency Plasma Treatment on the Characteristics of Polysulfonamide Membranes and the Intensity of Separation of Oil-in-Water Emulsions

Polysulfonamide membranes with a molecular weight cutoff of 20 kDa (pore size of 0.01 μm) have been treated with a flow of a radiofrequency (RF) capacitively coupled low-pressure glow discharge plasma in an argon and nitrogen atmosphere at an anode voltage of Ua = 1.5 kV and τ = 1.5 min. Instrumental methods of analysis have revealed the following changes in the structure of the membrane surface as a consequence of plasma treatment at the above parameters: a decrease in roughness, a decrease in the contact angle from 59.6° to 47.9°, and the formation of oxygen-containing functional groups. Experiments on the membrane separation of a 3% oil-in-water emulsion have been conducted; the results have shown that the use of plasmatreated polysulfonamide membranes leads to an intensification of the process.

Low pressure glow-discharge methanation with an ancillary oxygen ion conductor

Plasma technology is gaining increased interest for the reduction of carbon dioxide (CO2) to carbon monoxide (CO) and oxygen (O2). CO is a reaction partner with hydrogen (H2) to produce gas and fuel. This paper elaborates an improved method to produce methane (CH4) by plasma induced dissociation of carbon dioxide and H2 in one single setup. A low pressure glow discharge plasma with an integrated zirconia based ion conductor transports oxygen ions (O2−) in or out of the reaction chamber. Transporting oxygen ions into the reaction chamber is a way to have a controlled amount of water vapor for the conducted experiments. In contrast, leads the reduced amount of O2 ions to a theoretical decrease in the recombination of CO and O2 to CO2 in the ionized gas and therefore increases the CO2 conversion rate. The applied voltage to the ion conductor for the outward ion transportation and the power of the plasma source current have a major impact on the amount of extracted O2− ions. The effect of these parameters on the CO production rate and the formation of methane are investigated. A positive effect of the plasma current on the amount of CO and CH4 is detected. The influence of the temperature increase from the heated ion conductor relates to an undesired increase of the recombination rate of CO and O2 to CO2, but has a positive effect on the methanation.

Numerical simulation of discharge plasma generation and nitriding the metals and alloys

This research provides the numerical simulation of the plasma generation in a hollow cathode as well as the diffusion of nitrogen atoms into the metal in the low-pressure glow discharge plasma. The characteristics of the gas discharge were obtained and the relation of the basic technological parameters and the structural and phase state of the nitrided material were defined. Authors provided the comparison of calculations with the experimental results of titanium nitriding by low-pressure glow discharge plasma in a hollow cathode.

Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma

The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.

Inactivation of foodborne pathogens on the surfaces of different packaging materials using low-pressure air plasma

In the present study, low-pressure glow discharge plasma was used for surface decontamination of the common food packaging materials, namely glass, polyethylene, polypropylene, nylon, and paper foil. Low-pressure air plasma was generated over a vacuum pressure range of 0.5–5.0 Torr, and at a power density range of 12.4–54.1 mW/cm3. Compared to plasma-unexposed surfaces, no significant changes in optical properties, color characteristics, surface temperatures, tensile strengths, and deformation strains were observed with plasma-exposed surfaces. On plasma exposure of food pathogens-loaded packaging materials surfaces, as high as 4-log reduction (99.99%) in viable cell counts of tested food pathogens, especially Escherichia coli O157:H7 and Staphylococcus aureus, was observed within 5 min. And, the pathogens inactivation pattern can be better explained by Singh-Heldman model. Therefore, low-pressure air plasma was shown to be effective for inactivation of major foodborne pathogens, and different food packaging materials can be decontaminated using the plasma without adversely affecting their physical properties.

Measurements of helium 23S metastable atom density in low-pressure glow discharge plasmas by self-absorption spectroscopy of HeI 23S–23P transition

The helium 23S metastable atom densities are experimentally evaluated by self-absorption spectroscopy of the HeI 23S–23P transition spectra in two kinds of cylindrical glow discharge plasmas, which have different radii and are operated under different pressures of 300 and 20 Pa. The spectra are measured by using an interference spectroscopy system with a wavelength resolution of about 60 pm, and the relative intensities of the fine structure transitions are analyzed. It is found that the method is in principle applicable to plasmas with the pressure up to about the atmospheric pressure and electron density on the order of up to 1022 m−3. For a plasma with an absorption length of 10 mm and a spatially uniform temperature of 300 K, the method is sensitive to the metastable atom density roughly from 1016 to 1019 m−3.

Characterization of suprathermal electron population in He dc glow discharges by optical emission and probe diagnostics

Evidence of the strong contribution of electrons with energies up to the cathode fall potential was found in low-pressure He dc glow discharge plasmas (3–8 mTorr), in agreement with expectations from the estimates of the mean free path of electron–neutral inelastic collisions. A simple gridded probe, of the retarding field analyzer type, was applied to the characterization of the full electron energy distribution function (EEDF) in He plasmas with significant contribution from suprathermal electrons (up to 3.5%). The inferred EEDFs were cross-checked with results from the He line ratio diagnostic and good agreement was found at several values of pressure and plasma current.

Chemical and physical changes in surface of Argon plasma treated cotton fabrics

Hydrophilic cotton fabrics were exposed by low-pressure DC glow discharge plasma in argon atmosphere. The influence of different operating parameters such as treatment time, discharge potential, and operating pressure on the chemical and physical properties of the cotton fabrics is studied. Surface analysis and characterization of the plasma-treated cotton fabrics is performed using vertical wicking experiments, X-ray photoelectron spectroscopy, scanning electron microscopy, and weight loss measurements. The cotton fabrics show a significant increase in wicking behavior, an effect that increases with increasing treatment time. Results also show that low-pressure DC glow treatment leads to surface attrition of the cellulose fibers, accompanied by an incorporation of oxygen-containing groups (C–O, C=O, O–C–O, and O–C=O) on the cotton fibers.

Retracted: Study of the wettability of ZnO nanofilms

This article was mistakenly published twice. For this reason this duplicate article has now been retracted. For citation purposes please cite the original: http://www.inljournal.com/?_action=articleInfo&article=21 Al-doped and un-doped ZnO thin films deposited on quartz substrates by the nebulized spray pyrolysis method were studied to investigate the wettability of the surface. The main objective of the present study was to investigate the wettability of ZnO thin film by changing the concentration of Al doping. Microstructure and water contact angles of the films were measured by scanning electron microscopy (SEM) and using a contact angle goniometer. SEM studies revealed that the grain size within the film increases with the doping concentration. The contact angles were studied to see the effect of aluminum doping on the hydrophilicity of the film. ZnO films were found to be hydrophobic in nature. A good correlation was observed between the SEM micrographs and contact angle results. The nature of the film was found to change from being hydrophobic to hydrophilic after the treatment in low-pressure DC glow discharge plasma, which, however, was reversible with the storage time.

An atmospheric-pressure plasma brush driven by sub-microsecond voltage pulses

An atmospheric-pressure room-temperature plasma brush, which can deliver uniform surface treatment effects, is reported. The plasma structure, which includes the negative glow, Faraday dark space and positive column, is clearly visible to the naked eye. The width of the Faraday dark space diminishes with decreasing gap distance and this phenomenon is different from that observed from low-pressure glow discharge plasmas. High-speed photographs taken at an exposure time of 2.5 ns show that the plasma propagates from the nozzle to the object in about 100 ns and 10 ns for gap distances of 6 mm and 2 mm, respectively, and the results are consistent with electric measurements. The emission spectra reveal N2(B–A) bands in addition to those of O, , N2(C–B) and He, indicating that the plasma source is reactive and suitable for applications such as surface modification and materials processing.

Direct optical transition in plasma polymerized vinylene carbonate thin films

Plasma polymerized vinylene carbonate (PPVC) thin films were deposited on to glass substrates by low pressure glow discharge plasma from vinylene carbonate monomer at room temperature. Surface morphology and chemical structure of PPVC were analyzed by Scanning electron microscopy and Fourier transformation infrared spectroscopy, respectively. The surfaces of the PPVC thin films were observed to be smooth and pinhole free. The structural analysis by FTIR spectroscopy indicates structural rearrangement due to the removal of bonds. Ultraviolet-visible spectroscopic studies have been carried out on the PPVC thin films of different thicknesses. It is seen that the absorbance increases with the increase of film thickness. The direct band gap energies were calculated from the absorption data and are found to be in the range of 3.96 to 4.15 eV.

Surface morphology and chemical composition of lamb’s lettuce ( Valerianella locusta) after exposure to a low-pressure oxygen plasma

The influence of a low-pressure oxygen glow discharge plasma on secondary metabolites of lamb’s lettuce was examined. After extraction and hydrolysis the compounds were analysed by means of RP-HPLC. Whereas pure compounds showed a time-dependent degradation (flavonoids) or remained unchanged (phenolic acids), the exposure of lamb’s lettuce to the oxygen plasma led to a significant increase of protocatechuic acid, luteolin, and disometin after 120 s treatment time, independent of the applied plasma driving voltage. Contact angle (CA) measurements show an increased wettability of adaxial leaf surfaces after plasma exposure. A successive degradation of epicuticular waxes and cutin of the plant’s epidermis has been indicated by means of FTIR (ATR) and scanning electron microscopy (SEM). These findings suggest that reactive species in the plasma play a crucial role for the observed changes upon exposure to non-thermal plasma.

Why the local-mean-energy approximation should be used in hydrodynamic plasma descriptions instead of the local-field approximation

The local-mean-energy approximation (LMEA) and the local-field approximation (LFA) are commonly applied to include the electron properties like transport and rate coefficients into a hydrodynamic description of gas discharge plasmas. Both the approaches base on the solution of the stationary spatially homogeneous Boltzmann equation for the electron component, but the consequences of these approaches differ drastically. These consequences of using both the approaches are studied and discussed on a kinetic level and by comparison of results of hydrodynamic investigations of low-pressure glow discharge plasmas. It is found that the LMEA is to be strongly recommended for the application to a hydrodynamic description of dc as well as rf discharge plasmas, while the LFA is conditionally suitable to describe dc glow discharges with rough reaction kinetics only and its application to rf discharge plasmas is inappropriate.