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

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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

Atmospheric pressure plasma deposition of organosilicon thin films by direct current and radio-frequency plasma jets

Thin film deposition with atmospheric pressure plasmas is highly interesting for industrial demands and scientific interests in the field of biomaterials. However, the engineering of high-quality films by high-pressure plasmas with precise control over morphology and surface chemistry still poses a challenge. The two types of atmospheric-pressure plasma depositions of organosilicon films by the direct and indirect injection of hexamethyldisiloxane (HMDSO) precursor into a plasma region were chosen and compared in terms of the films chemical composition and morphology to address this. Although different methods of plasma excitation were used, the deposition of inorganic films with above 98% of SiO2 content was achieved for both cases. The chemical structure of the films was insignificantly dependent on the substrate type. The deposition in the afterglow of the DC discharge resulted in a soft film with high roughness, whereas RF plasma deposition led to a smoother film. In the case of the RF plasma deposition on polymeric materials resulted in films with delamination and cracks formation. Lastly, despite some material limitations, both deposition methods demonstrated significant potential for SiOx thin-films preparation for a variety of bio-related substrates, including glass, ceramics, metals, and polymers.This research was funded by EU H2020 M.Era-Net “PlasmaTex” project. Funding of the Romanian team was insured by the Romanian Ministry of Research and Innovation under the contract 31/2016/UEFISCDI. This work was funded by the Portuguese Foundation for Science and Technology FCT/MCTES (PIDDAC) and co-financed by European funds (FEDER) through the PT2020 program, research project M-ERA-NET/0006/2014. Slovenian team research was funded through the Ministry of Education, Science and Sport and Slovenian Research Agency (ARRS)

On the low electron density of an atmospheric pressure radio frequency plasma

A low temperature atmospheric pressure radio frequency plasma with planar electrodes structure is studied in terms of electron density for the use in biomedical applications. In the experiment, plasma can be ignited at power of 10 W and sustained in homogeneous α mode from 10W to 30W. Gas temperature is estimated based on determination of the rotational temperature of OH radicals. OH (A2Σ+→X2Π, 0-0) band from 306-312nm is detected and compared with simulated spectrum, giving the gas temperature as low as 375 ±25K under the input power of 30W, helium flow rate of 2 SLM. Line profile analysis is adopted to characterize the Stark broadening for Hβ line, further to obtain the electron density. Since we meet a situation of low electron densit y plasma, profiles with and without consideration of fine structure components are simulated, giving the estimated electron density around 8.3×1019m-3and 8.7×1019 m-3, respectively

Poly(3-hydroxybutyrate) Modified by Nanocellulose and Plasma Treatment for Packaging Applications

In this work, a new eco-friendly method for the treatment of poly(3-hydroxybutyrate) (PHB) as a candidate for food packaging applications is proposed. Poly(3-hydroxybutyrate) was modified by bacterial cellulose nanofibers (BC) using a melt compounding technique and by plasma treatment or zinc oxide (ZnO) nanoparticle plasma coating for better properties and antibacterial activity. Plasma treatment preserved the thermal stability, crystallinity and melting behavior of PHB‒BC nanocomposites, regardless of the amount of BC nanofibers. However, a remarkable increase of stiffness and strength and an increase of the antibacterial activity were noted. After the plasma treatment, the storage modulus of PHB having 2 wt % BC increases by 19% at room temperature and by 43% at 100 °C. The tensile strength increases as well by 21%. In addition, plasma treatment also inhibits the growth of Staphylococcus aureus and Escherichia coli by 44% and 63%, respectively. The ZnO plasma coating led to important changes in the thermal and mechanical behavior of PHB‒BC nanocomposite as well as in the surface structure and morphology. Strong chemical bonding of the metal nanoparticles on PHB surface following ZnO plasma coating was highlighted by infrared spectroscopy. Moreover, the presence of a continuous layer of self-aggregated ZnO nanoparticles was demonstrated by scanning electron microscopy, ZnO plasma treatment completely inhibiting growth of Staphylococcus aureus. A plasma-treated PHB‒BC nanocomposite is proposed as a green solution for the food packaging industry

Kaolinite Thin Films Grown by Pulsed Laser Deposition and Matrix Assisted Pulsed Laser Evaporation

In this work, thin films of lamellar clays were deposited by laser techniques (matrix assisted pulsed laser evaporation (MAPLE) and pulsed laser deposition (PLD)). The focus of this paper is the optimization of deposition parameters for the production of highly oriented crystalline films. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Contact angle measurements were employed to identify the wetting properties of the deposited thin films. Hydrophobic to superhydrophilic films can be prepared by using different deposition techniques and deposition parameters. MAPLE led to superhydrophilic films with contact angles in the range 4°–8°, depending on the microstructure and surface roughness at micro and nano scale. The 1064 nm PLD had a high deposition rate and produced a textured film while at λ = 193 nm an extremely thin and amorphous layer was depicted. Oriented kaolinite films were obtained by MAPLE even at 5 wt.% kaolinite in the target