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Diffuse Coplanar Surface Barrier Discharge in Artificial Air: Statistical Behaviour of Microdischarges

100%
Čech J., Hanusová J., Sťahel P., Černák M.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
Diffuse Coplanar Surface Barrier Discharge (DCSBD) is a novel type of atmospheric-pressure plasma source developed for high-speed large-area surface plasma treatments. The statistical behavior of microdischarges of DCSBD generated in artificial air atmosphere was studied using time-correlated optical and electrical measurements. Changes in behavior of microdischarges are shown for various electrode gap widths and input voltage amplitudes. They are discussed in the light of correlation of the number of microdischarges and the number of unique microdischarges’ paths per discharge event. The ‘memory effect’ was observed in the behavior of microdischarges and it manifests itself in a significant number of microdischarges reusing the path of microdischarges from previous half-period. Surprisingly this phenomenon was observed even for microdischarges of the same half-period of the discharge, where mechanisms other than charge deposition have to be involved. The phenomenon of discharge paths reuse is most pronounced for wide electrode
2
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Polylactic acid surface activation by atmospheric pressure dielectric barrier discharge plasma

88%
Hergelová B., Zahoranová A., Kováčik D., Stupavská M., Černák M.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
Polylactic acid (PLA) is suitable for applications in packaging and biomedicine due to its biodegradability. To improve PLA surface adhesion a plasma-chemical treatment using nonthermal plasma generated in ambient air via diffuse coplanar surface barrier discharge (DCSBD) was used. The optimal treatment time and power were investigated. Interaction between active plasma species and the polymer surface, and the resulting surface changes were studied by contact angle measurement, surface energy determination, FTIR, and XPS. The most hydrophilic surface was obtained after only 3–4 s treatment. Treatment up to 10 s did not damage the polymer but longer treatments (30 and 60 s) caused partial degradation. The plasma broke C-C/C-H bonds and formed more C-O, O-C=O and C-O-C bonds. During storage surface oxygen decreased and a negligible amount of nitrogen was adsorbed. The oxygen-containing functional groups probably sank into the PLA volume after treatment.
3
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Atmospheric pressure plasma treatment of polyamide-12 foils

88%
Hanusová J., Kováčik D., Stupavská M., Černák M., Novák I.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
The surface of a polyamide-12 (PA-12) foil was modified in order to improve the adhesive properties by two types of atmospheric pressure plasma sources. The samples were characterized using contact angle measurement, adhesive properties measurement and X-ray photoelectron spectroscopy (XPS). The ageing of the plasma modification was also studied. A significant increase in wettability was observed at different treatment times. The same effect was also seen in the adhesive properties - the adhesion was increased almost 12 times for 10 s DCSBD treatment in comparison to untreated PA-12. XPS analysis confirmed chemical changes due to the plasma modification of the PA-12. It was concluded that both plasma sources improve the adhesive properties of PA-12, with DCSBD obtaining better results.
4
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Layer-by-layer assembly of thin organic films on PTFE activated by cold atmospheric plasma

76%
Tóth A., Szentmihályi K., Keresztes Z., Szigyártó I., Kováčik D., Černák M., Kutasi K.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
An air diffuse coplanar surface barrier discharge is used to activate the surface of polytetrafluoroethylene (PTFE) samples, which are subsequently coated with polyvinylpyrrolidone (PVP) and tannic acid (TAN) single, bi- and multilayers, respectively, using the dip-coating method. The surfaces are characterized by X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Atomic Force Microscopy (AFM). The XPS measurements show that with plasma treatment the F/C atomic ratio in the PTFE surface decreases, due to the diminution of the concentration of CF2 moieties, and also oxygen incorporation through formation of new C–O, C=O and O=C–O bonds can be observed. In the case of coated samples, the new bonds indicated by XPS show the bonding between the organic layer and the surface, and thus the stability of layers, while the gradual decrease of the concentration of F atoms with the number of deposited layers proves the creation of PVP/TAN bi- and multi-layers. According to the ATR-FTIR spectra, in the case of PVP/TAN multilayer hydrogen bonding develops between the PVP and TAN, which assures the stability of the multilayer. The AFM lateral friction measurements show that the macromolecular layers homogeneously coat the plasma treated PTFE surface.
5
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Nonthermal plasma modification of polypropylene fibres for cementitious composites

76%
Morávek T., Fialová M., Kopkáně D., Ráheľ J., Sťahel P., Černák M.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
The plasma treatment of polypropylene fibres used as concrete admixtures for improving its mechanical properties is the focus of this research paper. A plasma treatment was conducted in a low-temperature plasma environment at atmospheric pressure in a DCSBD (Diffuse Coplanar Surface Barrier Discharge). The degree of hydrophilicity caused by the plasma treatment was determined by measuring the rate of penetration of water into the porous media, commonly referred to as the Washburn method. The influence of the addition of PP (polypropylene) fibres to the concrete matrix was investigated using a three point bending test which determined the flexural strength of concrete samples. Our experiments demostrate that plasma improves both the wettability of PP fibres and its adhesion to the concrete matrix. The tests of flexural strength show, that even a short plasma treatment (5 s) can have a significant impact on the mechanical properties of fibre-reinforced concrete composite.
6
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Chitosan immobilization to the polypropylene nonwoven after activation in atmospheric – pressure nitrogen plasma

76%
Černáková Ľ., Černák M., Tóth A., Mikulášová M., Tomašková M., Kováčik D.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
Atmospheric-pressure air and nitrogen plasmas generated by surface dielectric barrier discharges have been used to incorporate new functionalities at the surface of polypropylene nonwoven fabric. The main goals were to activate the polymer surfaces for subsequent immobilization of chitosan from water solution without using any crosslinking and wetting agents. The samples were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The nitrogen plasma treatment resulted in relatively high oxygen incorporation, about 9 atomic % mainly in aliphatic C=O type bonds and about 4 at.% of nitrogen incorporation in amine and other nitrogen functionalities. Chitosan was immobilized on the fabric fibers surfaces very homogeneously in amount of 2 - 5 g m-2. The chitosan coated samples exhibited a good laundering durability and strong antimicrobial activity against Bacillus subtilis and Escherichia coli.
7
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Properties of atmospheric pressure plasma oxidized layers on silicon wafers

76%
Skácelová D., Sládek P., Sťahel P., Pawera L., Haničinec M., Meichsner J., Černák M.
Open Chemistry
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2015
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vol. 13
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issue 1
EN
In this research a new process of plasma oxidation of crystalline silicon at room temperature is studied. The plasma oxidation was carried out using Diffuse Coplanar Surface Barrier Discharge (DCSBD) operating in ambient air and oxygen at atmospheric pressure. The influence of exposition time, plasma parameters and crystallographic orientation of silicon on oxidized layers and their dielectric properties were investigated. Thickness, structure and morphology of these layers were studied by ellipsometry, infrared absorption spectroscopy and scanning electron microscopy. During the treatment time, from 1 to 30 minutes, oxidized layers were obtained with thickness from 1 to 10 nm. Their roughness depends on the crystallographic orientation of silicon surface and exposure time. Electrical parameters of the prepared layers indicate the presence of an intermediate layer between silicon substrate and the oxidized layer.
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