Electron density diagnostics in atmospheric pressure radio frequency dielectric barrier discharge and discharge with bare electrode

Electron densities in two types of atmospheric pressure radio frequency plasma sources: dielectric barrier discharge (DBD) and discharge with bare electrode (DBE) are investigated by analysis of Stark broadening of Hydrogen Balmer (Hβ) lines. Voigt fitting is firstly employed to obtain the electron density below the theoretical lower limit of 1020 m-3. Fine-structure fitting method is further applied to verify the electron density for both plasma sources. When injecting power from 4 W to 20 W, the electron densities are found in the range of 2.9-6.1×1019 m-3 and 3.6-8.6×1019 m-3 for DBD and DBE, respectively. The electron density study aims to gain more insight of the physics of cold atmospheric pressure radio frequency helium plasma

Two-dimensional numerical simulation of a planar radio-frequency atmospheric pressure plasma source

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Electric field measurements in an atmospheric pressure radio frequency plasma using Stark polarization spectroscopy

Atmospheric pressure radio frequency(RF) plasma has been used not only in scientific research but also for industrial and medical applications, including surface cleaning, tooth root canal therapy, nanocomposite synthesis, etc. [1,2]. Though a lot of research has been performed on understanding this kind of plasma, the knowledge of its physics, especially RF electric field is still limited and in demand. Stark polarization spectroscopy is applied to investigate the electric field in an atmospheric pressure radio frequency helium plasma with a pin-sphere electrode geometry. Time resolved He I emission near electrode surface in an RF period is recorded and analyzed, as shown in figure 1 for grounded spherical electrode. Helium I lines at 492.19nm with allowed transition (2p 1Po–4d 1Do) and forbidden transition (2p 1Po–4f 1Fo) are observed and used for electric field calculation. Polarized π components of He I transitions, which are parallel to electric field, are selected through a linear polarizer. The distance between polarized field free allowed line and forbidden line is related to electric field imposing on the radiative helium atoms. Analysis of the He I emission allows to estimate time resolved electric field distribution in the sheath and bulk of the discharge. The electric field at the peak voltage near the grounded electrode ranges from 3.7±0.4 kV/cm to 94±3 kV/cm. This study aims to contribute to the atmospheric pressure radio frequency helium plasma physics

Non-uniform electric field diagnostics in an atmospheric pressure radio frequency helium plasma

Electric fields in the sheath region of an atmospheric pressure radio frequency (RF) helium plasma are studied through Stark polarization spectroscopy. Helium lines around 492 nm including the forbidden line and field-free line are observed and analyzed in order to investigate the Stark effect under electric field. A fitting method based on one field-free line and two forbidden line profiles is proposed to study the non-uniform electric field (high/ low field region) in the sheath. Time resolved electric field measurements are conducted for the sheath region at the grounded electrode. The high field region exhibits a peak and valley value around 33 kV/cm and 12 kV/cm. The low field region is characterized by a maximum and minimum value about 10 kV/cm and 6 kV/cm. The electric field and emission intensity approximately follow the current waveform in RF cycles. This work intends to contribute to the insight of electric field dynamics in the sheath of atmospheric pressure RF plasmas

Orange/red photoluminescence enhancement upon sf6 plasma treatment of vertically aligned zno nanorods

Although the origin and possible mechanisms for green and yellow emission from different zinc oxide (ZnO) forms have been extensively investigated, the same for red/orange PL emission from ZnO nanorods (nR) remains largely unaddressed. In this work, vertically aligned zinc oxide nanorods arrays (ZnO nR) were produced using hydrothermal process followed by plasma treatment in argon/sulfur hexafluoride (Ar/SF6) gas mixture for different time. The annealed samples were highly crystalline with ~45 nm crystallite size, (002) preferred orientation, and a relatively low strain value of 1.45 × 10−3, as determined from X-ray diffraction pattern. As compared to as-deposited ZnO nR, the plasma treatment under certain conditions demonstrated enhancement in the room temperature photoluminescence (PL) emission intensity, in the visible orange/red spectral regime, by a factor of 2. The PL intensity enhancement induced by SF6 plasma treatment may be attributed to surface chemistry modification as confirmed by X-ray photoelectron spectroscopy (XPS) studies. Several factors including presence of hydroxyl group on the ZnO surface, increased oxygen level in the ZnO lattice (OL), generation of F−OH and F−Zn bonds and passivation of surface states and bulk defects are considered to be active towards red/orange emission in the PL spectrum. The PL spectra were deconvoluted into component Gaussian sub-peaks representing transitions from conduction-band minimum (CBM) to oxygen interstitials (Oi) and CBM to oxygen vacancies (VO) with corresponding photon energies of 2.21 and 1.90 eV, respectively. The optimum plasma treatment route for ZnO nanostructures with resulting enhancement in the PL emission offers strong potential for photonic applications such as visible wavelength phosphors

The Interaction of Tungsten Dust with Human Skin Cells

In this chapter, we evaluate the tungsten (W) nanoparticle toxicity with respect to the normal human skin fibroblast cell. Tungsten dust formation is expected in the tokamak-type nuclear fusion installations, regarded as future devices for large-scale, sustainable, and carbon-free energy. This dust, composed of tungsten particles of variable size, from nanometers to micrometers, could be harmful to humans in the case of loss of vacuum accident (LOVA). In order to undertake the toxicity studies, tokamak-relevant dust has been deliberately produced in laboratory and afterward analyzed. Following that, cytotoxicity tests were performed using normal human skin fibroblast cell lines, BJ ATCC CRL 2522. Our study concludes that, at a low concentration (until 100 μg/mL), no cytotoxic effect of tungsten nanoparticles was observed. In contrast, at higher concentrations (up to 2 mg/mL), nanometric dust presents toxic effects on the cells

Plasma deposition of antibacterial nano-coatings on polymeric materials

Non-woven textile materials with antimicrobial properties are of high demands for applications ranging from medical dressing to everyday cleaning products. A plasma assisted route to engineer antimicrobial nano-composite coatings is proposed. Nano-particles of Ag, Cu and ZnO are tested as antimicrobial agents with average nano-particle size of 20-50 nm. Nanoparticles are incorporated in between two layers of an organosilicon film. The effect of the barrier coating on nano-particles release is determined by XPS. Antibacterial efficiency of the samples against P. aeruginosa ATCC 9027 and S. aureus M u50 bacteria shows that all treated samples exhibit higher antibacterial efficiency against S. aureus. The antibacterial efficiency of AgNPs and CuNPs is above 90% which is practically interesting for medical application while ZnONPs shows lower antibacterial efficiency.This work is supported by the M.Era-Net project IWT 140812 “PlasmaTex”.info:eu-repo/semantics/publishedVersio

Tungsten Nanoparticles Produced by Magnetron Sputtering Gas Aggregation: Process Characterization and Particle Properties

Tungsten and tungsten nanoparticles are involved in a series of processes, in nanotechnology, metallurgy, and fusion technology. Apart from chemical methods, nanoparticle synthesis by plasma offers advantages as good control of size, shape, and surface chemistry. The plasma methods are also environmentally friendly. In this chapter, we present aspects related to the magnetron sputtering gas aggregation (MSGA) process applied to synthesis of tungsten nanoparticles, with size in the range of tens to hundreds of nanometers. We present the MSGA process and its peculiarities in the case of tungsten nanoparticle synthesis. The properties of the obtained particles with a focus on the influence of the process parameters over the particle production rate, their size, morphology, and structure are discussed. To the end, we emphasize the utility of such particles for assessing the environmental and biological impacts in case of using tungsten as wall material in thermonuclear fusion reactors

Obtaining and Characterizing Alginate/k-Carrageenan Hydrogel Cross-Linked with Adipic Dihydrazide

The aim of this paper is obtaining and characterizing hydrogels based on different ratios of oxidized alginate (oA) and k-carrageenan (C), chemically cross-linked with adipic dihydrazide (adh). The alginate (A) was first oxidized with sodium metaperiodate in order to transform it into the dialdehyde derivative, a more reactive compound than alginate. A known procedure for oxidation of alginate with sodium metaperiodate in ethanol-water in order to improve alginate reactivity by transforming the hydroxyl end-groups into dialdehyde was used, preceded by a partially cleavage of the alginate chains. In the second stage, the mixture of dialdehydic derivative of oxidized alginate, k-carrageenan and glycerol subjected to reaction with adipic dihydrazide leads to a Semi-Interpenetrated Network covalently cross-linked alginate/k-carrageenan hydrogel (oACadh), based on the dihydrazone compound which is responsible for the chemical cross-linking. Pure alginate, k-carrageenan, oxidized alginate, adipic dihydrazide and the cross-linked hydrogel were characterized by: FTIR, XRD, and SEM