The Dielectric Barrier Discharge (DBD) is composed of many Filamentary Discharges (FDs), and it can be applied to ozone generation, gaseous pollution control, etc. In our laboratory, we investigated efficient cleaning methods of diesel exhaust gas by DBD. From the results of numerical simulation of chemical reactions, a homogeneous DBD was expected to improve the efficiency of pollution control and also the ozone yield. Recently, we found that a DBD device using alumina as barrier material can generate an Atmospheric Pressure Townsend Discharge (APTD) in air. In this research, we setup two ozonizers with different discharge modes of FD and APTD, and compared the ozone yield. The experimental results showed that the ozone yield was higher by the FD mode than by the APTD mode in lower Specific Input Energy (SIE) region. However in the region that the SIE is larger than 420J/L, the APTD mode showed higher ozone yield than FD mode.

An atmospheric pressure non-thermal equilibrium pin corona plasma jet was used to deposit polymeric coatings from monomer precursor in both vapour and liquid aerosol states to allow a direct comparison of the quality and performance of the as-deposited coatings, specifically with respect to the achievement of soft plasma polymerisation (SPP) where the coating exhibits minimal fragmentation or damage to the monomer molecule while, at the same time, being highly cross-linked. A long chain perfluorocarbon molecule was introduced into the helium plasma and coatings deposited at rates of up to 50 nm/min. XPS, FTIR, contact angle and ellipsometric measurements indicated that a controlled polymerisation reaction had taken place in the case of the vapour deposited samples through the vinyl group of the monomer, with only minor fragmentation of the functional perfluoro chain. Furthermore, a high level of cross-linking was achieved and the coatings were stable to a toluene wash. In contrast, while the liquid deposition samples showed good retention of monomer molecular structure, they exhibited negligible cross-linking and were readily removed by immersion in toluene rendering them functionally useless.

In this paper the use of a floating interelectrode for dielectric barrier discharge (DBD) plasma actuators applied in aerodynamics is described. The velocity profiles of airflow generated by a single-DBD actuator with the floating interelectrode are presented. Also double-DBD and multi-DBD plasma actuators with floating interelectrodes were investigated to get a longer DBD on a dielectric surface. Obtained results show that the DBDs with floating interelectrodes are capable of extending the plasma area on the dielectric surface. The airflow induced by the successive DBD sets with floating interelectrodes in the multi-DBD actuator had the same direction enhancing the net airflow. The airflow velocity produced by the investigated multi-DBD actuator was up to 10 m/s. This suggests that multi-DBD actuators with floating interelectrodes can be attractive for many aerodynamic purposes.

Results of our experimental investigation on the ozone zero phenomenon suggested us the importance of the electrode surface condition. This means that the main cause of the phenomenon, that is, temporal decrease of ozone concentration at the outlet of DBD type ozone generator and the recovery characteristics from the phenomenon are considered as the surface reaction process, which are influenced strongly by the surface condition. The surface condition is never constant during the ozone generation and varies gradually or remarkably with time depending on the experimental conditions. Therefore we have been continued to make clear the cause of the phenomenon, for example, the reproducibility of the phenomenon, using new electrodes and together with the surface analysis technique etc. In this paper, we describe on the above results and discussion.

Combination of two old-yet-new technologies (plasma and catalyst) is getting attentions for the advanced processes in 21 century. This paper reports the complementary combination of atmospheric pressure nonthermal plasma with catalyst for the air pollution control application. The most important feature of this complementary combination is that plasma enables catalyst to work even at room temperature. Up-to-date data on catalyst screening for the cycled system will be given in terms of enhancement factor and adsorption capacity. Visual observation using ICCD camera was applied to study how discharge plasma interacts with catalyst at atmospheric-pressure and ambient temperature.

Plasma medicine is a new medical field with first very promising practical studies. However, basic research needs to be done to minimize risk and provide a scientific fundament for medical therapies. Therapeutic application of plasmas at or in the human body is a challenge both for medicine and plasma physics. Today, concepts of tailor-made plasma sources which meet the technical requirements of medical instrumentation are still less developed. To achieve selected effects and to avoid potential risks, it is necessary to know how to control composition and densities of reactive plasma components by external operation parameters. Therefore, a profound knowledge on plasma physics and chemistry must be contributed by physical research. Therapeutic applications required cold, non-thermal plasmas operating at atmospheric pressure. These plasmas are a huge challenge for plasma diagnostics, because usually they are small scale, constricted or filamentary, and transient. Regarding the manageability in everyday medical life, atmospheric pressure plasma jets (APPJ) and dielectric barrier discharges (DBD) are of special interest for medical applications. Working in open air atmospheres, complex plasma chemistry must be expected. Considering that, a great deal of effort combining experimental investigation and modelling is necessary to provide the required knowledge on plasma sources for therapeutic applications.

We have applied the Ion Mobility Spectrometry/Mass Spectrometry (IMS/MS) and the Atmospheric Pressure Chemical Ionisation/Mass Spectrometry (APCI/MS) techniques to study the formation of the ions in the positive corona discharge (CD) in highly purified nitrogen with impurities at 100 ppt level. The main products observed were H3O+(H2O)n ions (reduced ion mobility of 2.15 cm2 V-1 s-1). Additionally, we have observed ions with reduced mobilities 2.42 cm2 V-1 s-1 and 2.30 cm2 V-1 s-1. The intensity of these ions was increasing with the increasing discharge current. We associated these peaks with NH4+ and NO+(H2O)n. The formation of these ions results from trace amounts of O2 and NH3 in nitrogen. The time evolution of the ions in corona discharge has been studied using the APCI/MS technique in the time windows ranging from 100 μs to 2 ms. The present work indicates the ability of the IMS technique equipped with CD ions source to detect impurities below 100 ppt level.

Gaseous Helium at 300 K and pressure (0.1–3) MPa was excited using a corona discharge both for negative and positive high voltages. The light emitted from the ionization zone of the discharge was analyzed. Asymmetric shape of atomic lines 706 nm and 728 nm was recorded. Blue wings of the lines are more intensive than their red wings. The line shape is described as a convolution of Lorentz profile of the line center and a quasi-statistical profile of a blue wing of the line. Such analysis predicts no heating of the gas in the ionization zone for positive corona and considerable heating for negative corona.

This paper presents simulations of the dynamics of surface charging by an air plasma discharge at atmospheric pressure initiated by a needle anode inside a capillary glass tube. During the discharge propagation in the tube, the highest positive surface charge density is observed close to the point electrode. We have shown that during the discharge propagation, the positive surface charge is increasing behind the discharge front, while the electric field at the surface is decreasing. Then, we have studied the influence of the tube radius, its permittivity and the applied pulsed voltage on surface charges. We have shown that the surface charge density during the discharge propagation is inversely proportional to the tube radius and surface charge densities of 30–50 nC/cm2 for a tube with Rtube = 100 μm and an applied voltage of 12 kV have been obtained. We have also noted that a higher permittivity results in a higher surface charge density and a faster surface charge deposition. Then we have shown that the surface charge deposited is proportional to the applied voltage. Finally, at the end of the voltage pulse, our simulations indicate that the positive surface charge deposited during the discharge propagation in the tube decreases to very low values in few nanoseconds.

Using phenol as a model organic pollutant we studied and characterized an innovative advanced oxidation process in water using a prototype dielectric barrier discharge (DBD) reactor in which electrical discharges are produced in the air above the water surface. Phenol is decomposed quite efficiently in this reactor operated at room temperature and atmospheric pressure. The process selectivity to form CO2 is, however, to be improved since a large fraction of the treated organic carbon is unaccounted for. The rate of phenol conversion increases linearly with the reciprocal of the pollutant initial concentration, suggesting the operation of a mechanism of inhibition by products as found earlier for oxidation of volatile organic pollutants in air plasmas.

In modern medicine human mesenchymal stem cells are becoming increasingly important. However, a successful cultivation of this type of cells is only possible under very specific conditions. Of great importance, for instance, are the absence of contaminants such as foreign microbiological organisms, i.e., sterility, and the chemical functionalization of the ground on which the cells are grown. As cultivation of these cells makes high demands, a new procedure for cell cultivation has been developed in which closed plastic bags are used. For adherent cell growth chemical functional groups have to be introduced on the inner surface of the plastic bag. This can be achieved by a new, atmospheric-pressure plasma-based method presented in this paper. The method which was developed jointly by the Fraunhofer IST and the Helmholtz HZI can be implemented in automated equipment as is also shown in this contribution. Plasma process gases used include helium or helium-based gas mixtures (He + N2 + H2) and vapors of suitable film-forming agents or precursors such as APTMS, DACH, and TMOS in helium. The effect of plasma treatment is investigated by FTIR-ATR spectroscopy as well as surface tension determination based on contact angle measurements and XPS. Plasma treatment in nominally pure helium increases the surface tension of the polymer foil due to the presence of oxygen traces in the gas and oxygen diffusing through the gas-permeable foil, respectively, reacting with surface radical centers formed during contact with the discharge. Primary amino groups are obtained on the inner surface by treatment in mixtures with nitrogen and hydrogen albeit their amount is comparably small due to diffusion of oxygen through the gas-permeable bag, interfering with the plasma-amination process. Surface modifications introducing amino groups on the inner surface turned out to be most efficient in the promotion of cell growth.

Microdischarges in a surface barrier discharge with special asymmetric needle-needle arrangement were investigated by means of cross-correlation spectroscopy (with sub-ns and sub-mm resolution) and an intensified CCD camera equipped with a far field microscope. The surface barrier discharge was driven at conditions (overvoltage) resulting in several microdischarges per half period of the applied sinusoidal voltage. At these conditions and in this arrangement regular patterns of microdischarges between the two electrodes points are formed due to local charging of the dielectric surface. The cross-correlation spectroscopy setup enables the recording of microdischarge development for different phases of the applied voltage. Distinct differences in the microdischarge development between the subsequent phase channels in the positive half period can be observed, while the first channel shows similar behavior as in the single-microdischarge mode which was conducted recently.