Degradation in aluminium and copper foil electrodes in surface dielectric barrier discharges (sDBDs), operating in ambient air, is studied using various microscopic methods. It is determined that difference in the oxidation dynamics for these two materials lead to different morphology of the exposed electrode edge. The structure of the exposed electrode, in its turn, affects the dynamics of the microdischarges and the main integral electrical characteristics of the sDBD: power input, charge amplitude, shape of the charge−voltage cycle plot.

A stepwise propagation of a guided streamer along a helium atmospheric pressure plasma jet driven by a dielectric barrier discharge was recorded. To feed the plasma jet, we used a power supply generating an output voltage signal consisting of a superposition of 41.6 kHz bipolar square pulses and 300 kHz oscillating signals. At a positive half a period of the output voltage signal, a step-by-step propagation was observed for the ionization wave along the plasma jet. The streamer head stops with the decrease in voltage in the first cycle of oscillations and then restarts its motion at the voltage front of the next cycle of a voltage oscillation. The streamer propagation velocity and plasma jet length are likely to be controlled by varying the gas flow rate, bias voltage, voltage rise rate, frequency of oscillations in the pulse, and other parameters.

No abstract

No abstract

Lazukin A., Serdukov Y., Pinchuk M., Stepanova O., Krivov S., Syubushkina I. (2018): Treatment of spring wheat seeds by ozone generated from humid air and dry oxygen. Res. Agr. Eng., 64: 34-40.The paper presents an analysis based on conflicting data regarding the results of the treatment of soft spring wheat seeds by ozone generated from humid air and dry oxygen. Morphological characteristics of treated seeds (the length of a sprout, the total length of roots and the sprout-to-root ratio), 7-day germination ability along with the extent of 7-day-old seedlings contamination are considered in terms of ozone concentrations. The experiments were conducted using the wheat seeds of 2013 and 2014 yields. For the same concentrations of ozone, morphological characteristics of treated seeds and efficiency of seed surface treatment changed similarly for both ways of ozone production. However, the efficiency of seeds treatment and stimulation of seeds germination with ozone are not correlated; and the germination ability of the seeds is not changed after ozone treatment.

No abstract

The experimental results of the surface barrier discharge plasma products effect on soft winter wheat seeds in electrode configurations consisted of the parallel strips at a distance of 5 and 10 mm from each other are shown. In each electrode system, the seed treatment was carried out for 10, 60, 120 and 180 s at the sinusoidal voltages of 1.8, 2.1, 2.4 or 2.7 kV with the frequency of 4.4 kHz applied to the electrodes. The seeds were placed in one layer on the grounded plane at the distance of 10 mm from the dielectric barrier surface. The treatment effect was estimated by the morphological characteristics of 3-day seedlings. To control the airflow in the gap, the particle imaging visualization method was used. It is shown that treatment modes are divided into two principal groups. The first group represents the modes when the airflow reaches the plane on which the seeds are located, the second group represents the modes when the airflow does not reach this plane. In the first case (the distance between the strips is 10 mm, the voltage is 2.4−2.7 kV at all exposures), it is possible to achieve modes that stimulate germination. Seed germinating ability did not change and maintained high values at all considered modes.

No abstract