Argon Plasma Discharge Research Articles

Calculation of temperature conditions of a plasma sputtering cell for decontamination of nuclear power plant constructions

We are developing a technology for the “dry” deactivation of nuclear power plant constructions by ion sputtering of surfaces with micro-sized radioactive contaminants, our technology is implemented by plasma discharge in an inert gas medium with mass transfer of sputtered material and its deposition in diffusion mode on the anode substrate. Unlike traditional radiochemical methods, in our technology, radionuclides do not transfer into liquid radioactive waste, but condense in a compact solid form, which makes possible to use them. Весаuse our technology can be applied both during decommissioning nuclear power plants (including deactivation of neutron-irradiated nuclear graphite), and during routine operation and scheduled repairs of nuclear reactors, so it is possible to extract the necessary isotope concentrate in the required quantities, due to intense neutron flux in nuclear power plant. The design of plasma sputtering cell to remove radionuclides from the irradiated graphite and NPP construction surfaces involves ignition of a direct current plasma discharge in an inert gas (for example, argon) at the pressure of P ~ 0.1–1 atm and control of the temperature conditions of the sputtering material deposition. In this paper temperatures of the anode (tantalum collector) and the cathode (sputtered graphite) were calculated depending on the input power to the argon plasma discharge. Data on temperatures of cathode and anode (collector) surfaces make it possible to control the elemental composition of the sputtered atoms and to form nanoscale layers of radionuclide concentrate on collector for using in radiation medicine and new beta-voltaic batteries. Thus, the technology is important not only for the deactivation of nuclear power plants, but also for the formation of nanoscale layers of beta-active materials.

Structure and Properties of Silumin Surface after Vacuum Arc Plasma-Assisted Deposition of Coatings Irradiated by Low Energy High Current Pulsed Electron Beam

The paper presents the results of modification of the silumin surface layer using a multicycle processing technique which combines the formation of the film (titanium)-substrate (silumin) system and the low energy high current pulsed electron beam (LEHCPEB) irradiation of submillisecond duration in one cycle. A KOMPLEX plasma-ion-assisted electron-beam setup (Institute of High Current Electronics SB RAS, Tomsk, Russia) is used for silumin treatment. Titanium is used as an alloying element. The thickness of the deposited film is 0.5 μm in each alloying cycle, the number of which is 1, 5 and 10. Surface alloying includes ion-bombardment cleaning and heating by hot and hollow cathodes of argon plasma discharge, with negative bias voltage supply to the specimen (initial heating up to preset temperature, surface cleaning and activation); plasma-enhanced chemical vapor deposition of metal films (argon is used as a carrier gas); and LEHCPEB irradiation of the film (titanium)-substrate (silumin) system. It is shown that multicycle alloying of the grade АK12 silumin (G-AlSi12, DIN, Germany) with titanium leads to a dissolution of silicon and intermetallic inclusions in the surface layer up to 30 μm thick, the formation of submicro- and nanocrystalline multiphase structure with the microhardness and wear resistance, which are 1.4 and 14.2 times higher than in cast silumin.

Measurement of temperature of a dusty plasma from its configuration

AbstractA new concept called “configurational temperature” is introduced in the context of dusty plasma, where the temperature of the dust particles submerged in the plasma can be measured directly from the positional information of the individual dust particles and the interaction potential between the dust grains. This method does not require the velocity information of individual particles, which is a key parameter to measure the dust temperature in the conventional method. The technique is initially tested using two‐dimensional (2D) OpenMP parallel molecular dynamics and Monte Carlo simulation and then compared with the temperature evaluated from experimental data. The experiment have been carried out in the Dusty Plasma Experimental (DPEx) device, where a 2D stationary plasma crystal of melamine formaldehyde particles is formed in the cathode sheath of a DC glow discharge argon plasma. The kinetic temperature of the dust is calculated using the standard particle image velocimetry technique at different pressures. An extended simulation result for the three‐dimensional case is also presented, which can be employed for the temperature measurement of a three‐dimensional dust crystal in laboratory devices.

Magnetron plasma modification by sputtering copper target of electrospun fluoropolymer material to possess bacteriostatic properties

Abstract Polymer matrices from the copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) were successfully formed by the method of electrospinning. The matrices were successfully modified by DC magnetron sputtering of the copper target in the argon plasma discharge. To investigate the morphology and elemental composition of VDF-TeFE matrices, the following methods were used: scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), correspondingly. The results of SEM showed that polymer matrices consist of chaotically interlaced fibers whose diameters range from 0.2 to 1.4 μm. Using the EDX method, it was determined that as the modification time increases, the F/C ratio decreases, and the Cu/O increases. To study the wettability, the marginal angles were measured by the interaction of the surface with water. The wetting angle varies from 125.1° to 130.9°. Investigation of antibacterial properties has revealed that the polymeric matrix with modification time 120 s has bacteriostatic properties.

Високочастотна плазма при атмосферному тиску як засіб осадження тонких плівок

The main units of the industrial high-frequency generator have been modernized. The design and technical coordination of the plasma torch impedance was developed in order to obtain high-frequency plasma with capacitive coupling for the transmission of electrical energy at atmospheric pressure. The data on the main elements of the structures of adapted units are given, their functional purpose is indicated. Special attention is paid to the principles of operation of the modified units of equipment and their functional relationship when controlling the process of synthesis of films for nanotechnology. The reasons why nanotechnology is not widespread on the existing high-frequency capacitive plasmatrons are analyzed. New effects of high-frequency plasma and ways to improve the plasmatron for deposition of thin films were discovered. A theoretical justification for the effect of working substance transfer in a plasma channel (cord) of a high-frequency capacitive discharge is found. The possibility of ignition of a single-electrode high-frequency flare discharge from a plasma of a high-frequency capacitive discharge is experimentally proved. An explanation of the structure of high-frequency flare discharge under these conditions is given. The possibility of using the near-electrode spot of the torch for the vapor concentration of the working substance and the deposition of the film is revealed. The main regularities for the synthesis of nanofilms on the example of zinc and aluminum oxides are investigated. Pyrolysis is chosen among plasma chemical reactions to prepare a pair of working substances. Plasma luminescence of high-frequency capacitive discharge is studied for the purpose of effective plasmochemical reactions in the channel of argon plasma discharge and steam supply of the working substance to the substrate. Thin layers of Al2O3 and ZnO are synthesized by a new method using high-frequency argon plasma at atmospheric pressure.

Plasma-prepared arsenic telluride films: relationship between physico-chemical properties on the parameters of the deposition process

Previously, we demonstrated the principal possibility to synthesize arsenic telluride films of different chemical and phase composition by PECVD when we directly use elemental arsenic and tellurium as the precursors. This paper presents the results of systematic study of physicochemical properties of As-Te films prepared in low-temperature non-equilibrium RF (40 MHz) argon plasma discharge at low pressure (0.1 Torr) as well. The surface morphology, structure and thermal crystallization behavior of the films obtained were studied in dependence on the plasma parameters of the deposition process. The characteristics of stationary and transitional photoconductivity of the films have been studied as well.

The spatial-temporal distribution of the electron density and temperature in nanosecond pulsed discharge plasma measured by laser Thomson scattering

The spatial-temporal distribution of the electron temperature (Te) and density (ne) in a nanosecond pulsed discharge (NPD) argon plasma with a ball-to-plate electrode configuration at 2 × 103 Pa has been measured by Laser Thomson Scattering (LTS). The peak voltage between two electrodes is 1520 V and the current is 3 A when the ball-like electrode is connected to the negative high voltage. The results indicate that it is possible to enhance the electron density of the plasma discharge using the rising edge of pulse voltage. The measured plasma parameters: Te decreases exponentially from 1.75 eV to 0.1 eV and ne increases rapidly to 3.94 × 1020 m−3 from 15 ns to 115 ns then decreases to 1.17 × 1019 m−3. In the discharge with cylindrical geometric symmetry, Te increases from ball to plate, while ne is opposite. In the r-direction, both Te and ne decrease from central to edge at 3.4 mm. Value of ne varies by 20 times from maximum to minimum and Te is only about 1.5 times.

Plasma-Driven Reactive Species Production and Transport in a 2-D Discharge Cell

A 2-D cell was employed to study the plasma–liquid interface. Chemical probes were used to compare the chemical reactivity induced by both air and argon plasma discharges in bubbles. Methyl orange and potassium iodide-starch solutions were used to visualize the propagation of acidic and oxidative fronts into the bulk liquid beyond the interface. Acidic and oxidative fronts were observed for both air and argon plasmas, indicating that charge exchange and electron impact processes at the interface are crucial to plasma-induced reactivity in liquids. Absorption spectrophotometry of indigo trisulfonate was performed to measure the transport of oxidative species, primarily aqueous ozone, and hydroxyl radicals, from plasma to the liquid region. Chemical reactivity at the interface can be transported far into the bulk liquid region due to plasma-induced fluid flow.

Surface modification of PVA thin film by nonthermal atmospheric pressure plasma for antifogging property

In this work, a polyvinyl alcohol (PVA) thin film was modified by exposure to a dielectric barrier discharge argon plasma. The plasma was generated by a sinusoidal power supply with discharge voltage of 4.75 kV (rms), and frequency of 30 kHz at duty cycle 6.13%. The effect of the plasma on the PVA thin film was investigated by analyzing the contact angle, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and UV–visible spectroscopy. After the plasma treatment, the contact angle was found to be decrease from 29.6 ± 0.4° to 14.5 ± 0.2°, which implied that the surface property had changed to a hydrophilic state caused by an increase in the surface roughness and introduction of oxygen, including a polar carbonyl group. It was found that the plasma-treated hydrophilic PVA thin film exhibited excellent antifogging and highly transparent characteristics, making it an appropriate material for food packaging and green houses.

The Electrical Characteristic of Plasma Discharge by Using Different Operating Conditions in Vanadium Sputtering System

This paper report the experimental results of the effects of the inter-electrode distances and applied voltages for various operating pressure on the electrical characteristic of plasma discharge. We have studied the Current-voltage (I-V) characteristics and discharge current – gas pressure (I-P) for different inter-electrode gaps (3, 4, 5, 6, and 8) cm of the planar magnetron discharge. Also Paschen curve were measured at different spacing, The Paschen curves in Ar gas show that the breakdown voltage between two electrodes is a function of pd (The product of the pressure inside the chamber and distance between the electrodes). The results show the sensitivity of electrode separation lead to change the electrical characteristic of generating plasma; where The I-V characteristics of argon gas were deduced as a plasma system operated in abnormal glow discharge region, which is very impotent deposition sputtering. As well as the discharge current was increased for argon plasma discharge with the increasing of the working pressure lead to increase the deposition rate. Paschen curve is analyses at different working pressures and gap distances between two electrodes .the behavior between discharge current and discharge voltage for different gap distances between two electrodes was nonlinear, In addition the experimental finding validated that the suitable electrical characteristics of glow discharge current as a function to applied voltage for varying argon gas pressure at inter-electrode spacing equal to 5 cm.

Low-temperature plasma treatment of polylactic acid and PLA/HA composite material

Investigations of the surface physicochemical properties of polylactic acid and polylactic acid/hydroxyapatite composite in a 70/30 ratio modified by atmospheric pressure low-temperature glow discharge argon plasma with the pulse duration of 1 μs and 5 μs and repetition rate of 100 kHz are described. Plasma modification of such materials may significantly affect physicochemical properties of surface. The polymerization of l-lactide was carried out at a temperature of 155 °C for 6 h. X-ray diffraction analysis shows that the degree of crystallinity of polylactic acid and composites based on polylactic acid/hydroxyapatite composite increases after plasma treatment due to polymer chain disruption. Infrared spectroscopy indicates that the –C=O absorption band intensity increases with plasma pulse duration, in turn indicating oxidation processes occurring in the polylactic acid surface layers. The wettability characteristics of the materials are improved by the plasma treatment, resulting in decreased water, glycerol, and ethylene glycol contact angle, and enhanced free surface energy.

Argon plasma-treated fluorinated ethylene propylene: Growth of primary dermal fibroblasts and mesenchymal stem cells

Surface modification is an important step in making a synthetic polymer cytocompatible. We have previously reported improved cytocompatibility of immortalized human keratinocytes (HaCaT) with the otherwise bioinert fluorinated ethylene propylene (FEP) upon treatment with argon plasma discharge. In this article, we show that FEP modified with Ar plasma with the power of 3 and 8 W for 40 and 240 s served as a suitable material for cultivation of primary human dermal fibroblasts (HDF), which showed significantly improved proliferation and spreading comparable to standard tissue culture polystyrene. We also evaluated focal adhesions formed by HDF cells on modified FEP, which were far more numerous compared to pristine FEP. Moreover, we attempted spontaneous osteogenic differentiation of adipose-derived mesenchymal stem cells modified with human telomerase reverse transcriptase on Ar plasma-modified FEP. While the spontaneous osteogenic differentiation was unsuccessful, the cells were able to adhere and differentiated on tested matrices upon the administration of osteodifferentiation medium. These combined findings suggest that the treatment of FEP with Ar plasma comprises and efficient method to enable the adhesion and proliferation of various cell types on an otherwise largely bioinert material.

Effect of Nitrogen Addition on Electron Density and Temperature of Cascaded Arc Argon Discharge Plasma Diagnosed by Laser Thomson Scattering

The electron density and electron temperature of the recombining argon plasma from a cascaded arc discharge source were measured by the laser Thomson scattering approach. In this paper, a small amount of nitrogen gas was introduced into the argon discharge source. The addition of the nitrogen gas was applied to investigate the change of the plasma parameters in terms of electron density and temperature. The measurements showed that the electron density dropped by 2 orders of magnitude at 10% nitrogen gas addition compared with no nitrogen addition. The dissociative recombination following the charge transfer between atomic ions and nitrogen molecules was responsible for the decrease of electron density. In addition, with the increase of nitrogen gas addition, the measurements indicated that the electron temperature first increased to a maximum and then decreased. This was due to that the superelastic collision between the electrons and the highly excited vibrational nitrogen molecules could heat the electrons leading to the increase of electron temperature while the electron-vibrational energy transfer by electron–nitrogen molecules impact excitation resulted in that electron temperature decreased due to electrons’ kinetic energy losing processes.

Carbon nanostructures grafted biopolymers for medical applications

ABSTRACTEnhancing biopolymers with carbon nanostructures leads to the creation of attractive materials suitable for diverse medical application. We studied surface properties and cytocompatibility of amine functionalised carbon nanoparticles (CNPs) grafted on biopolymer film. Poly-L-lactic acid and poly-3-hydroxybutyrate were treated in an inert argon plasma discharge and subsequently grafted with three types of amine-functionalised CNPs. The surface properties of (i) CNPs and (ii) grafted CNPs were studied using multiple methods. BET, electrokinetic and XPS analyses confirmed the successful grafting of amino-compounds on the surface and also into the pores of CNPs. Goniometry approved the binding of the modified CNPs on the polymer surface. From AFM is evident that both the biopolymers show completely changed surface morphology after grafting of CNPs. The cytocompatibility test with vascular smooth muscle cells showed that the presence of the modified CNPs on polymer substrates has a more positive effect on cytocompatibility of PLLA rather than PHB.

Diagnostics of low-pressure capacitively coupled RF discharge argon plasma

Low-pressure capacitively coupled RF discharge Ar plasma has been studied using Langmuir probe. The electron temperature, electron density and Debay length were calculated under different pressures and electrode gap. In this work the RF Langmuir probe is designed using 4MHz filter as compensation circuit and I-V probe characteristic have been investigated. The pressure varied from 0.07 mbar to 0.1 mbar while electrode gap varied from 2-5 cm. The plasma was generated using power supply at 4MHz frequency with power 300 W. The flowmeter is used to control Argon gas flow in the range of 600 standard cubic centimeters per minute (sccm). The electron temperature drops slowly with pressure and it's gradually decreased when expanding the electrode gap. As the gas pressure increases, the plasma density rises slightly at low gas pressure while it drops little at higher gas pressure. The electron density decreases rapidly with expand distances between electrodes.

Experimental verification of modified Paschen’s law in DC glow discharge argon plasma

Breakdown voltage of a gas is the required voltage to start a discharge or electric arc through the gas. Paschen’s law describes the characteristics of gas breakdown voltage between two electrodes. This law states that the Gas breakdown voltage(VB) depends only on the product of gas pressure (p) and gap length(d) between electrodes (VB=f(pd)). In this paper, the effect of electrode separation length(d) and electrode radius (r) on gas breakdown voltage is studied experimentally. A gas discharge system with a large gap length compared to electrode radius is used for the study. Paschen curves are plotted for different electrode separation lengths and electrode radii. It is observed that gas breakdown voltages deviates from Paschen’s law and depend on the d/r ratio also in addition to the product of gap separation and pressure, i.e. VB=f(pd,d/r). This relation, already reported in the analyses of micro gap discharge and theoretical studies, is known as modified Paschen’s law. In order to experimentally verify the modified Paschen’s law in large discharge gaps, many experiments are conducted by varying both electrode separation and electrode radii but keeping the d/r ratio always same. It is observed that for different discharge system geometries, if d/r ratio is same, the break down voltages are same for same pd value. The Paschen’s curves are also plotted for different experiments and it is observed that the curves overlap if d/r ratio is set same for all experiments. Thus, the work presented in this paper experimentally verify the modified Paschen’s law.

Diagnostics of low-pressure discharge argon plasma by multi-optical emission line analysis based on the collisional-radiative model

This work is focused on diagnostics of electron temperature (1.0 eV–3.8 eV) and electron density (1.0 × 109 cm−3–5.0 × 1012 cm−3) of low-pressure (133 Pa) discharge argon plasma by optical emission spectroscopic (OES) measurement. The diagnostic method using multi-emission lines was analyzed. First, the excitation-kinetic models were obtained by extracting dominant kinetic processes based on the collisional-radiative model. Then, the diagnostic equations for wide range of electron temperature and density were proposed to describe the approximate excitation kinetic balance of several excited levels. 15 optical emission lines (wavelength range: 340.7 nm–912.3 nm) were selected for OES measurement. RMS of the theoretical relative error was found to be 5.96% for electron temperature, while 32.6% for electron density. The diagnostics of 2.45 GHz microwave plasma was demonstrated by the proposed method and by the probe method. The electron density results by the proposed method were in good agreement with the probe method.

A Comparative Study of Surface Modification of PS Films Using DC Glow Discharge Plasma in N2 and Ar

In this paper, the polystyrene (PS) film surface was treated using DC glow discharge nitrogen (N2) and argon (Ar) plasma to improve the wettability and antibacterial properties. The untreated and plasma treated surfaces were characterized by contact angle, FTIR, XRD and SEM analysis. The antibacterial activity of untreated and plasma treated PS films was evaluated using optical density (OD) technique against Staphylococcus aureus bacteria. The results of the PS film surface treated in both N2 and Ar showed a noticeable increase in the wettability due to the increase in the roughness and the introduction of oxygen-containing polar groups as corroborated with SEM, weight loss calculations and FTIR spectra. The results of antibacterial activity showed that the treated samples inhibit the bacterial growth. The Ar treatment created more oxygen-containing polar groups and increase roughness on the PS film surface and extensively modified the polymer surface than the N2 treatment.

Enhancement of IR transparency of arsenic sulfide materials via plasma-chemical conversion of the initial arsenic monosulfide in low-temperature RF plasma

For the first time the direct conversion of arsenic monosulfide (As4S4) in low-temperature non-equilibrium radio frequency (40 MHz) argon plasma discharge at low pressure (0.1 Torr) was studied in terms of the preparation of arsenic sulfide films of different chemical content. In this case, arsenic monosulfide was used as the only precursor. The degree of arsenic monosulfide conversion, and, respectively, the chemical content of the samples was varied through a change of plasma parameters—the electron density and the temperature in the plasma discharge. The optical emission spectra of plasma of the (Ar–As4S4) mixture at different energy inputs were studied to clarify the routes of initiation of chemical interaction. The possible mechanism has been assumed. The expansion of the IR transparency window due to the change of structural properties of the materials in the plasma was investigated and discussed.

Surface treatment with non-thermal humid argon plasma as a treatment for allergic contact dermatitis in a mouse model

PurposeCold plasma generated at atmospheric pressure has attracted intense interest in biomedical applications. However, studies of cold plasma in dermatology, and as a possible therapy for non-infectious skin diseases, including burn and wound healing, psoriasis, and allergic contact dermatitis (ACD) etc., are still quite scarce. The present study reports the treatment of ACD in vivo, using a non-thermal humid plasma source in a mouse model and shows the latter could be a potential alternative approach for therapy of ACD and other inflammatory skin diseases. MethodsThe model of ACD on the mouse back was induced by a solution of DNFB and treated by argon plasma containing small amounts of either N2, O2, or H2O. The developments of ACD regions were photographed and histopathological analysis by H&E-staining was performed. ResultsThe best effect was obtained using humid plasma (H2O addition), where the ACD symptoms decreased after one or two 1-min plasma treatments. Even for severe ACD with ulcers and crust formation, the humid plasma-treated mice recovered faster than the control group. ConclusionsThe therapeutic ability of the humid argon plasma discharge was proposed to be induced by reactive oxygen species (HxOy) transported from the discharge zone, which are adhesive and accumulate on the skin surface, penetrating the subcutis to eliminate inflammation. However, in treatments using plasma with addition of oxygen or nitrogen (without water) the active gaseous species are blocked due to poor adhesion to and penetration into the dry ACD skin, with correspondingly poor treatment effects. The enhanced in vivo healing in ACD mice indicate the non-thermal humid plasma could be a potential alternative approach for therapy of ACD and other inflammatory skin diseases.