P. Špatenka

Germination of Chenopodium Album in Response to Microwave Plasma Treatment

The seeds of Lambs Quarters (Chenopodium album agg.) were stimulated by low-pressure discharge. The tested seeds were exposed to plasma discharge for different time durations (from 6 minutes to 48 minutes). Germination tests were performed under specified laboratory conditions during seven days in five identical and completely independent experiments. Significant differences between the control and plasma-treated seeds were observed. The treated seeds showed structural changes on the surface of the seat coat. They germinated faster and their sprout accretion on the first day of seed germination was longer. Germination rate for the untreated seeds was 15% while it increased approximately three times (max 55%) for seeds treated by plasma from 12 minutes to 48 minutes.

Synthesis of aligned carbon nanotubes by DC plasma-enhanced hot filament CVD

Abstract Vertically aligned carbon nanotubes (CNTs) films have been prepared by a direct current plasma-enhanced hot filament chemical vapour deposition method. The growth of multi-walled carbon nanotubes on metal (Fe, Co, Ni) precoated silicon substrate are studied between 500 and 1000 °C using gas mixtures of methane, hydrogen and argon. The influence of substrate pre-treatment, substrate voltage and deposition temperature on the structure and the alignment of the CNTs are discussed. In dependence on thickness of the thin metal layers, thermal pre-treatment or hydrogen plasma etching and plasma parameters during the deposition process different carbon nanostructures, especially regarding tube diameter, morphology and arrangement could be proved. Transmission electron microscopy images of isolated tubes showed an imperfectly trained tubular structure of graphite shells, formed as ‘bamboo’-like shapes with partly crystalline metal droplets on the tip. Because the alignment of the tubes is induced by the discharge voltage and the electrical field, the characteristic plasma parameters as plasma potential, electron energy and electron density, measured by Langmuir probe investigations were discussed.

New Physicochemical Treatment Method of Poppy Seeds for Agriculture and Food Industries

Poppy seeds (Papaver somniferum L.) are often attacked by various fungal diseases, and their field germination rate is low. The aim of this experiment was to increase the germination rate and growth of seedlings by modifying the poppy seeds using cold plasma discharge. The seeds were treated in a Plasonic AR-550-M under power of 500 W with argon gas flow of 50 mL/min, oxygen gas flow of 50 mL/min for different time durations in seconds (0, 180, 300, 600, 1800, 3000, 4200, and 5400). The seed germination rate and growth of the seedlings were recorded. Cold plasma positively affected the seed germination rate for time exposure between 180~3000 s. Seedling acceleration on the sixth day of the experiment showed the highest values at exposure 180~600 s. Cold plasma seems to be a good physicochemical way to modify seeds without chemical agronomical application.

How various plasma sources may affect seed germination and growth

Germination and early growth of buckwheat (Fagopyrum aesculentum) after low-temperature plasma discharge treatment in air gas generated in various devices were tested. Three pre-treatment times were used: 180 s, 300 s and 600 s. Seed cultivation was carried out in laboratory conditions. Number of germinating seeds was counted, length and weight of seedling sprouts were measured. The data were analysed with two-way ANOVA: a significant influence of the type of plasma apparatus, time of exposure and combination of both factors were found. A positive effect on germination and early growth was observed after the application of GlidArc device (low-temperature plasma generated in air gas under atmospheric pressure between two electrodes). The opposite effect of surface dielectric barrier discharge (SDBD) apparatus, which is characterized by plasma with high power density, was observed. Shorter pre-treatment times for SDBD device must be therefore used. Effects of seed germination and early growth of seeds strongly depended on the type of the used plasma apparatus.

A comparison of internal plasma parameters in a conventional planar magnetron and a magnetron with additional plasma confinement

This paper deals with Langmuir probe measurements in a planar magnetron sputtering system in which the plasma confinement near a target can be improved by means of an assembly of permanent magnets placed above the target. The electron density, electron temperature, plasma and floating potentials and electron distribution function are measured in various positions between the target and a substrate under various conditions in the discharge. Our experiments proved that the additional magnetic confinement leads to approximately two times higher electron density and strong enhancement (by about an order of magnitude) of the electron temperature in almost all positions of the deposition system investigated.

Low-pressure RF multi-plasma-jet system for deposition of alloy and composite thin films

A plasma-chemical reactor with a multi-plasma-jet RF hollow-cathode system has been developed for the deposition of alloy and composite thin films. Two primary plasma-jet channels and one secondary plasma channel were created in the volume of the reactor. High-density plasma flowing in these plasma-jet channels is generated inside the nozzles. These work simultaneously as RF hollow cathodes. An RF hollow cathode discharge is generated in these nozzles and is subsequently blown out of the reactor, creating flowing plasma jets. These jets were used for the deposition of SiGe and ZrCN thin films as an example of the deposition of alloy and composite thin films with this system. Co-sputtering or reactive co-sputtering of the nozzle material using high-density RF hollow-cathode plasma was applied for the deposition process. Control of the composition of the thin films was accomplished by setting the relative distance between the nozzle outlets without changing the plasma density inside the RF hollow cathodes. The composition of films was investigated with an electron microprobe system equipped with an X-ray microanalyser. This apparatus allowed quantitative analysis of the films. The stoichiometric homogeneity of the films was studied with this technique. Optical emission spectroscopy was used to investigate the secondary plasma-jet channel.

Process control of plasma polymerization in a large industrial reactor

Abstract Application of the triple-probe method for volume-resolved monitoring of electron density and electron temperature during industrial-scale polymerization plasma process was tested. As a model process, simultaneous deposition of barrier film on the inner wall of six bottles using an asymmetrical r.f. discharge was investigated. The reproducibility of the process was better than 94%. The plasma density differed between particular bottles up to a factor of 2, and this difference increased with pressure. The barrier properties of the film increased with the product of the ion current and square root of the electron temperature

Photocatalytic Activity of Nanostructured Titanium Dioxide Thin Films

The aim of this paper is to investigate the properties and photocatalytic activity of nanostructured TiO2 layers. The glancing angle deposition method with DC sputtering at low temperature was applied for deposition of the layers with various columnar structures. The thin-film structure and surface morphology were analyzed by XRD, SEM, and AFM analyses. The photocatalytic activity of the films was determined by the rate constant of the decomposition of the Acid Orange 7. In dependence on the glancing angle deposition parameters, three types of columnar structures were obtained. The films feature anatase/rutile and/or amorphous structures depending on the film architecture and deposition method. All the films give the evidence of the photocatalytic activity, even those without proved anatase or rutile structure presence. The impact of columnar boundary in perspective of the photocatalytic activity of nanostructured TiO2 layers was discussed as the possible factor supporting the photocatalytic activity.

PES fabric plasma modification

Polyester ranks the upper position in the world fiber production — nearly 54% of the total production of synthetic fibers. Troubles connected with minimizing of the textile hydrophobicity are usually being solved by the textile fibers’ surface chemical modification, but from ecological point of view modification of fabric with low temperature plasma is superior to classical chemical wet processes. Application of various plasmas for PES treatment has been already described. To compare the effectiveness of different plasma sources we performed a series of experiment both in RF and MW plasmas. For working gas nitrogen, oxygen and their mixtures were employed. Internal plasma control was provided by measurement of optical emission spectra. The hydrophilicity degree was determined by the drop test. Paper discusses optimal conditions of the PES fabric plasma treatment.

Application of atmospheric corona discharge for PES fabric modification

Polyester fabrics belong to often and regularly used materials in the textile industry. Traditional, mostly chemical methods of their processing often join with undesired environmental problems. The ecological requirements oblige to search and explore new and environmentally safer methods or technologies. One of them might be the cloth surface modification by means of atmospheric corona discharge. Paper presents connection between modification characteristics such as corona power input, duration of action, electrode optimisation and cloth sorption. It shows that the corona-modified cloth has an increased sorption and, probably, the touch.