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Plasma treatment impact on physical and chemical properties of polymeric fibers
Hlůžek, R. ; Prošek, Z. ; Trejbal, J. ; Fládr, J. ; Potocký, Štěpán
Presented work focuses on chemical and physical properties of plasma modified polymeric macro-fibers. Polyethylene terephthalate (PET) and polypropylene (PP) fibers having approx. 300 mu m in diameter were modified using cold oxygen plasma in order to achieve their surface changes needed for durable bond and adhesion with cement matrixes. A duration of plasma modification differed between 5 to 480 seconds, where an effect of the treatment was examined. Fiber surfaces chemical changes were researched via wettability measurement with demineralized water (the measurement was repeated immediately and after 1, 7 and 30 days to find out the changes stability). Physical changes were studied by means of weight balance (determination of weight loss) and tensile strength tests. It was found that wettability was enhanced significantly - up to two times, while mechanical properties of treated fibers decreased only slightly.\n
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Performance of cement composites reinforced with surface-modified polypropylene micro-fibers
Antoš, J. ; Dejdar, L. ; Trejbal, J. ; Prošek, Zdeněk
This paper focuses on the mechanical properties investigation of cement pastes reinforced with surface treated polymer fibers. The cement matrix was composed of Portland cement (CEM I 42.5 R, w/c ratio equal to 0.4). Two polypropylene fiber types (micro-and macro-fibers) were used as randomly distributed and oriented reinforcement in volume amount of 2 %. The fibers were modified in the low-pressure inductively coupled cold oxygen plasma in order to enhance their surface interaction with the cement matrix. The investigated composite mechanical properties (load bearing capacity and response during loading) were examined indirectly by means of four-point bending mechanical destructive tests. A response of loaded samples containing treated fibers were compared to samples with reference fibers. Moreover, cracking behavior development was monitored using digital image correlation (DIC). This method enabled to record the micro-cracks system evaluation of both fiber reinforced samples.\n
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The Influence of Surface Treatment and Activation of Thin Film Composite Membranes with Plasma Discharge and Determination of Their Physicochemical Properties.
Slepička, P. ; Setničková, Kateřina ; Petrusová, Zuzana ; Slepičková-Kasálková, N. ; Kolská, Z. ; Siegel, J. ; Jansen, J. C. ; Esposito, E. ; Fuoco, A. ; Švorčík, V. ; Izák, Pavel
In this work we have focused on the surface treatment and activation of membranes (73 AC and 82 V) with plasma discharge and determination of their physicochemical properties. The surface morphology, wettability, zeta potential of pristine and plasma- treated membranes were tested and compared.
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Modification of polymeric substrates by means of non-equilibrium plasma
Kuzminova, Anna ; Kylián, Ondřej (advisor) ; Čech, Vladimír (referee) ; Novák, Stanislav (referee)
Title: Modification of polymeric substrates by means of non-equilibrium plasma Author: Anna Kuzminova Department: Department of Macromolecular Physics Supervisor of the doctoral thesis: doc. RNDr. Ondřej Kylián, Ph.D. Abstract: Processing of polymeric materials by means of non-equilibrium plasma is a topic that reaches increasing attention, which is due to the wide range of possible applications. As an example can be mentioned processing of polymeric foils used for food packaging, where plasma treatment enables to improve their functional properties (e.g. increase their printability or enhance their barrier properties). In the frame of this PhD. thesis two different strategies suitable for the modification of polymeric materials were followed. The first one was based on treatment of polymers by atmospheric plasma. The main attention was devoted to the investigation of influence of atmospheric pressure plasma on surface properties of 8 commonly used polymers, namely on their chemical composition, morphology and wettability. In addition, it was observed that plasma treatment causes also alteration of their mechanical properties, may lead to their substantial etching and in some cases improves their biocompatibility. The second studied strategy was based on coating of polymers with thin functional...
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Effect of Plasma Oxidation of Carbon Working Electrode on Its Electrochemical Response
Koporec, Lukáš
Screen-printed electrochemical sensors are very perspective because they are much smaller than common electrodes used in electrochemistry, portable, ecological and can be very easily modified in order to increase their sensitivity and selectivity for specific analytes. In this study, plasma treatment was used to modify the carbon working electrode of a screen-printed threeelectrodes system. Plasma treatment was performed using RF plasma discharge in argon/oxygen atmosphere. The plasma modified electrodes exhibited considerable enhancement in electrocatalytic activity towards studied electroactive compounds.
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Plasmochemical treatment of photoanodes with semiconducting oxide layer
Ďurašová, Zuzana ; Zita, Jiří (referee) ; Dzik, Petr (advisor)
This diploma thesis deals with a plasmochemical treatment of photoanodes with an active layer containing TiO2 deposited on two different substrates by material printing. The plasmochemical treatment was performed by a low-temperature ambient-air plasma using a diffuse coplanar surface barrier discharge (DCSBD). The experimental part is focused on the investigation of DCSBD influence on the fabricated photoanodes photoelectrochemical properties, and the influence of plasma treatment time. Process optimization was achieved by height adjustment of the electrode. The processed coatings were electrochemically investigated by linear sweep voltammetry and chronoamperometry.
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Preparation and Plasmachemical Reduction of Model Corrosion Layers on Iron.
Sázavská, Věra ; Novák, Stanislav (referee) ; Zahoranová, Anna (referee) ; Krčma, František (advisor)
The plasmachemical removal process of corrosion layers is based on a reduction effect of RF hydrogen low-pressure plasma, and it is used for archaeological objects. Incrustation layers on artifact surface become brittle and porous due to plasma processing. The structure and composition of corrosion layers is changed. Therefore, it is much easier to recover the original surface of the plasma treated artifacts in contrary to those treated by conventional ways. Moreover, we can save time on invasive and thus dangerous mechanical removal of corrosion layers as for example sanding is. After plasma treatment, we can observe fine details of the original surface and memory of tools used during its manufacturing. These details are important information on the origin and manufacturing methods of the artifacts. The plasma reduction process leads to the removal of impurities from cavities as well, and a function of mechanical components of archaeological object can be restored. Moreover, chlorides can be easily removed from the corrosion layers and thus any significant post-corrosion is protected. Each archaeological object is original and it has its own “corrosion history”. First, the object had been exposed to the atmosphere for a long time. Then, it had been often placed in a tomb or grave or it otherwise got into the soil or sea. Thus, each archaeological object was exposed to different corrosion stress (humidity, composition of corrosive environment, etc.). Due to these facts, any universal way of a corroded object treatment is very difficult or even impossible to propose. In this work, the problem was solved using model samples of common metals which were treated at various plasma treatment conditions. Archaeological objects made of iron are the most common artifacts, and the typical corrosion products on iron are akaganeite, rokuhnite, and szomolnokite. These three corrosion products were created on the model samples in laboratory and then, the plasmachemical reduction was applied for their removal. The experiment was done in a Quartz cylindrical reactor with capacitive coupled RF plasma created using outer electrodes. We used discharge power from 100 W to 400 W in a continuous or pulsed regime (duty cycle of 75 %, 50 % and 25 %). Flowing plasma was created in pure hydrogen at pressure of 150200 Pa. Sample temperature was monitored by a thermocouple, and it did not exceed 200C during all these experiments. This temperature is regarded as a limit temperature for metallographic changes of archaeological iron. Higher temperature can cause destruction of archaeological iron objects. The optical emission spectroscopy of OH radical was used for the process monitoring. We focused on the monitoring of OH-radicals generated in the plasma, which are characteristic species formed by this process. Each corrosion product has a different time evaluation of generated OH-radicals, which is closely related to the degradation of a given corrosion product. Corrosion layers were analyzed before and after the plasmachemical reduction by SEM-EDX. We have found that the plasmachemical reduction is not very suitable for the szomolnokite corrosion product, which is degraded with difficulty and at high applied powers, only. However, very good removal efficiency was obtained for the rokuhnite and akaganeite corrosion.
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Plasma surface modification of powder fillers
Štulrajterová, Lujza ; Bystřický, Zdeněk (referee) ; Přikryl, Radek (advisor)
This bachelor’s thesis deals with the study of particulate-filled composite materials and the influence of filler surface modifications on the properties of the composite. Important aspects of particulate fillers, used fillers and possible surface treatments were characterized in the theoretical section of this work. Dimethacrylate matrix with halloysite nanotubes as filler was chosen as a studied system. The filler was modified by low-temperature plasma under low pressure and by silanization. Surface of the modified filler was studied by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Particle size distribution was measured by photon cross-correlation spectroscopy and dynamic light scattering (DLS). Mechanical properties of prepared particulate composites were established by the testing of the flexural properties. Fracture areas were analyzed by using scanning electron microscopy (SEM). The results showed no effects of the plasma treatment on the mechanical properties. Silane treatment of the filler surface illustrated improvement of the composite material strength.
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Fotokatalytické vlastnosti plazmově zpracovaného oxidu wolframového
Brožek, Vlastimil ; Domlátil, J. ; Mastný, L. ; Šrank, Z. ; Janča, J. ; Eliáš, M.
Tungsten trioxide with the band gap about 2.58 eV is known as a material, which a photocatalytic effect after UV-radiation exposure can be observed. However, in some cases more detailed material specification and the consideration of its complex structural and stoichiometric uniqueness are lacked in its photoactivity data. The presented work is focused on the study of tungsten trioxide samples photoactivity using the unified method that determines the reference substances colour changes after 360 nm UV-radiation exposure. The samples were prepared by from ammonium paratungstate treated in oxygen or argon plasma, which was generated by capacitive coupled RF generator operated at low partial pressures. The differences in oxygen stoichiometry which depends on total temperature plasma, because especially the presence of hydrogen coming from the ammonium cation disintegration causes a partial reduction partly to the WO2.7 oxide.
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