A uniform plume with pulsed discharges is generated through using a plasma brush excited by a direct current power supply. The results indicate that the plume length increases with the increasing gas flow rate or dissipated power. The optical emission spectrum from the plasma brush reveals that active species are abundant in the plasma plume. Based on the spectrum, an electron density on the order of 1014 cm−3 is obtained, which increases with the increasing dissipated power and gas flow rate. After a single scan of the plasma brush on the polyethylene terephthalate surface, a uniform surface modification is achieved with an improved hydrophilic width of about 24 mm. The water contact angle of the surface decreases with the decreasing scanning velocity and nozzle-sample distance or the increasing dissipated power and gas flow rate. Moreover, the treated surface shows an aging behavior in 6 days. Raman spectra indicate that oxygen-containing polar groups are generated on the treated polyethylene terephthalate surface. The polar groups are contained in oxidized materials, which are observed by scanning electron microscopy.

Liquid-cathode discharge at atmospheric pressure has been excited by a direct current voltage above the surfaces of deionized and tap water. Gap voltage decreases with increasing discharge current, which suggests that the discharges above both the liquids belong to a normal glow regime. For a given discharge current, gap and power voltages of the discharge above deionized water are higher than those above tap water. The optical spectrum obtained from the water surface reveals that there are abundant active species related to oxygen, nitrogen, and water vapor, which leads to changes in the pH value, conductivity, and concentrations of NO3−, NO2−, and H2O2 in liquid. Therefore, these parameters are investigated in the two liquids as functions of discharge current and plasma activation time. For both of them, the results show that the pH value decreases, while conductivity increment and concentrations of NO3−, NO2−, and H2O2 increase with increasing discharge current or activation time. Compared to activated tap water, deionized water has a lower pH value, while higher conductivity increment and concentrations of NO3−, NO2−, and H2O2 are observed after the same activation time and discharge current. Finally, these parameters are compared for different salt types and salt concentrations after plasma activation.

Using a one-dimensional fluid model, period multiplication and chaos behaviors in the time domain are numerically investigated in atmospheric pressure helium dielectric-barrier discharge excited by a modulated sinusoidal voltage. The results indicate that with the increasing duty ratio of the modulated voltage, various nonlinear behaviors are obtained, including asymmetric single-period, period-three, period-seven, chaotic, and symmetric single-period states. More details are revealed that period-four, period-nine, and period-thirteen states can also be observed between period-three and period-seven states. For the period-three state, there are six current pulses in each current period, which have different amplitudes with each other. Besides the duty ratio, the sinusoidal frequency of the modulated voltage is varied, which results in similar nonlinear behaviors. Additionally, under a duty ratio of 80%, it maintains a stable period-two state with the increasing voltage amplitude or the decreasing gap width. During this process, the pulse number and duration time increase per half voltage cycle. Finally, spatial distributions of the electric field, electron density, and ion density are investigated for the novel period-three state, which is qualitatively explained through analyzing the influence of the averaged density of electrons and metastable states just before the discharge moments.