Ozone production in a planar dielectric barrier discharge (DBD) in atmospheric oxygen in different discharge modes was investigated. Results show that the gas temperature in discharge channel depends ...strongly on discharge mode, with a value of 300–310 K in glow regime and 440–465 K in streamer regime. Ozone production yield in glow DBD is much higher than that in streamer one, with the best yield of 342.6 and 162.6 g/kWh, respectively. Gas temperature in discharge channel relates to the effective discharge area of DBD, which is a small fraction of the whole electrode surface in streamer DBD compared with nearly the whole surface in glow DBD. The gas temperature in the channel plays a decisive role in the conversion of oxygen atoms to ozone as well as the ozone equilibrium concentration. Excellent performance of glow DBD demonstrates the high energy efficiency and reliability for practical application of planar DBD-based ozone generator.
Trichel pulses of negative corona discharge in atmospheric air are investigated in a needle-to-plate configuration. Time-resolved images of the pulsed discharge are recorded by using an ICCD camera. ...Light emission spectra of N2 molecules and N2+ ions during the discharge are measured by optical diagnostics. The distributions of the positive N2+ ions and the reduced electric field along the discharge channel are analyzed accordingly. The results show that the positive ions that can accumulate in space and distort the electric field play an important role on the formation of the Trichel pulse. The Trichel pulse is a mode transition between low-current Townsend discharge and high-current glow discharge. The rising time of the pulse corresponds to the breakdown and formation of glow discharge, and the decay time is related to destroy the process of positive ion clouds and the quenching of glow discharge. The time interval between the pulses is determined by the re-accumulation of positive ions near the cathode in the low-current Townsend discharge to form the positive ion clouds as well as a strongly-distorted electric field.
Regulating the parameters of the atmospheric pressure plasma jet (APPJ) is meaningful for industrial applications. Since plasma is a typical functional fluid in the magnetic field, it is possible to ...control the discharge characteristics via the Lorentz force. In this study, the effects of a locally divergent magnetic field on the generation and propagation of APPJ were examined experimentally. The experiments used a coplanar dielectric barrier discharge (CDBD) device driven by a 30 kHz AC high-voltage source to generate a helium APPJ. A locally divergent magnetic field of 250 mT (maximum) was applied coupled with the electric field, and noticeable enhancement was observed. The results showed that the magnetic field changed the motion state of electrons and promoted collision ionization, leading to a 40% improvement in the APPJ length (0.6 cm) and a 23% increase in the intensity of line O (777.2 nm). In addition, the spatiotemporal evolution and flow field of APPJ were diagnosed by ICCD and schlieren technique. The combination of electric and magnetic fields may effectively optimize the APPJ in practical applications.
In this paper, we report a nitrogen (N) doped zinc oxide (N:ZnO) film grown by the reactive high power impulse magnetron sputtering (HiPIMS) technique on glass substrates, where nitrogen gas (N2) is ...used as the N source. The proposal is to investigate the influence of process parameters on the alteration of the N:ZnO film from n- to p-type conductivity and the stability of the p-type behavior. It is obtained that the n- or p-type behavior of the as-deposited N:ZnO film is affected by the N2 flow rate, deposition temperature, and inductively coupled plasma (ICP) assistance, of which the ICP assistance had a great impact. It is noticed that, owing to the improved ionization rate of the N2 dopant by ICP, the N:ZnO film almost totally prefers to exhibit p-type behavior. Based on the measurement by temporal resolution optical emission spectroscopy, the components in plasma are obtained and the ion reaction in film growth is confirmed: a high concentration of active N+ in the ICP-assisted plasma reacts with sputtered Zn+ in vapor to form No defect in the p-type N:ZnO film. We then forecast that a stable p-type N:ZnO film can be grown using the HiPIMS technique.
This paper explores the predominant mechanisms for the deviation of micro-gap dc gas breakdown and the transition between different mechanisms as the electrode separation d changing under a ...pin-to-plate electrode configuration using 2d3v particle-in-cell simulation with Monte Carlo collisions. The deviated breakdown characteristic curves as a function of d or gas pressure p are investigated and both present a plateau region. Through researching the position of discharge path, it is found that a self-modulation effect manages to maintain the breakdown voltage at the minimum value defined by Paschen’s curve in a certain d or p range and forms the plateau. The ranges of d and p for the plateau are also established. Theoretical calculation on the secondary electron emission coefficient induced by ion-enhanced field and determined by a surface roughness factor confirms that the ion-enhanced field emission effect affects the breakdown voltage significantly when d is below a critical value. The smaller the surface roughness factor is, the smaller the critical d will be. Under this effect, the breakdown voltage is decreased with d decreasing (also referred to as an increasing left branch with d increasing). Conclusively, the deviation characters of micro-gap gas breakdown are controlled by different mechanisms at different d ranges. The predominant mechanism for the deviation is the self-modulation effect, serving as the main reason for the plateau region, at moderate d of several micrometers and will transit to the ion-enhanced field emission effect, which is responsible for the increasing left branch at smaller d.
Physico-chemical and biological effects of atmospheric pressure plasmas (APPs) find numerous applications in biotechnology, medicine, and other fields. Recent studies revealed APPs’ potential for ...ischemic stroke treatment through the protection of neuronal cells from injuries. However, the mechanisms of the plasma neuroprotection effects still remain unknown. This study reveals the key mechanisms of APP plasma jet (APPJ) enabled reduction of neuronal cell death caused by oxygen and glucose deprivation (OGD) under stroke-relevant conditions. Plasma reduced OGD induced apoptosis of SH-SY5Y neuronal cells is based on reactive oxygen and nitrogen species production and on nitric oxide related activation of the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase G (PKG) pathway, followed by the Bcl-2/Bax level modulation and caspase3/9 activity inhibition. In addition, the protective effect of APPJ treatment on OGD injured SH-SY5Y cells could be abolished by cGMP pathway inhibitor LY83583 pretreatment. Collectively, our findings highlight that the mechanism of the neuroprotection effects of the plasma treatment is closely related to the intracellular cGMP/PKG pathway, which provide experimental and theoretical references for future studies on plasma medicine.
Negative corona discharge occurs widely in high voltage transmission lines and other “high voltage” uses, which can cause strong electromagnetic interference (EMI). In this research, the pulse ...current of multi-needle negative corona discharge and its electromagnetic (EM) radiation characteristics were studied and compared with that of single-needle negative corona discharge. A dipole radiation model was established to analyze the EM radiation characteristics of the negative corona discharge. The results show that the Trichel pulse discharge process of one discharge needle in multi-needle discharge structure will inhibit the discharge of the other discharge needles. It is only when the voltage reaches a certain threshold will the current and EM radiation fields of multi-needle discharge structure with a significant increasing of amolitude. The frequency of EM radiation of negative corona discharge is not affected by the number of needles, but is only related to ambient air pressure. This research provides a basis for detecting corona discharge sources in different conditions.
The DC corona discharge in air and the induced ionic wind were investigated in the needle-to-water system at atmospheric pressure. The water deformation was measured under various conditions, and ...wind pressure and active areas were estimated accordingly. The effects of applied voltage, gap spacing and tip radius on the corona ionic wind were studied and the qualitative analysis was provided. Self-rotation of corona discharge was observed in experiments. The results show that higher voltage or electric field strength results in a stronger ionic wind. The active area increases with applied voltage below a voltage threshold. There is an optimal gap distance for a wider as well as stronger ionic wind and blunter needle we used leads to an enhancement on both the active area and the wind strength. The wind velocity reaches 7 m/s at optimized condition in the present system. The rotation of corona discharge helps to improve the active area and uniformity of the treating area which may be associated with the chemical reaction of the water surface.
•We exam the ionic wind by DC corona discharge at atmospheric pressure.•Voltage has a positive effect on ionic wind strength and active area.•There is an optimal gap distance for a wider as well as stronger ionic wind.•Blunter needle enhances both the active area and the wind strength.•A rotation phenomenon of corona is observed and discussed.
Besides a typical high‐density plasma source, electrical explosion of conductors is also indispensable in switches, nanomaterial synthesis, shock‐wave sources, etc. In this paper, an experimental ...study regarding plasma dynamics of electrical wire explosions (μs‐timescale) is presented, with spatiotemporal resolved diagnostics. Pure Cu/Ni wire and Cu‐Ni alloy wire were used and compared. The alloy wire usually has a higher resistivity, resulting in a higher initial energy deposition (heating) rate. Abel inverse transformation indicated that the plasma radiation focussed on the outer region of the discharge channel for the alloy wire. In addition, the metallic vapour determined by the material properties had a considerable influence on the plasma process and resulting nanomaterials. In particular, both transverse and axial‐layered structures were observed in alloy wire vapour. In addition, for the first time, the expanding arc‐like plasma of explosion products was understood and examined from aspects of material properties and energy relaxation. The later stage of wire explosion resembled the state of regular metal vapour arcs under 1 MPa pressure. Finally, the core factor for the fast energy deposition stage of wire explosion was ascertained. Correlations between pre‐exposition circuit parameters and post‐explosion dynamic effects were found, which is significant for practical applications.
Previous studies suggest the potential efficacy of neuroprotective effects of gaseous atmospheric-pressure plasma (APP) treatment on neuronal cells. However, it remains unclear if the neuroprotective ...properties of the gas plasmas benefit the ischemic stroke treatment, and how to use the plasmas in the
ischemic stroke models. Rats were subjected to 90 min middle cerebral artery occlusion (MCAO) to establish the ischemic stroke model and then intermittently inhaled the plasma for 2 min at 60 min MCAO. The regional cerebral blood flow (CBF) was monitored. Animal behavior scoring, magnetic resonance imaging (MRI), 2,3,5-triphenyltetrazolium chloride (TTC) staining, and hematoxylin and eosin (HE) staining were performed to evaluate the therapeutic efficacy of the gas plasma inhalation on MCAO rats. Intermittent gas plasma inhalation by rats with experimental ischemic stroke could improve neurological function, increase regional CBF, and decrease brain infarction. Further MRI tests showed that the gas plasma inhalation could limit the ischemic lesion progression, which was beneficial to improve the outcomes of the MCAO rats. Post-stroke treatment with intermittent gas plasma inhalation could reduce the ischemic lesion progression and decrease cerebral infarction volume, which might provide a new promising strategy for ischemic stroke treatment.
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