Atmospheric Pressure Plasma Jet Source Research Articles

Helium Atmospheric Pressure Plasma Jet Source Treatment of White Grapes Juice for Winemaking

In the last few years, new emerging technologies to develop novel winemaking methods were reported. Most of them pointed out the need to assess the barrel aging on the wine product, fermentation process, green technologies for wine treatment for long term storage. Among these, plasma technologies at atmospheric pressure are on the way of replacing old and expensive methods for must, wine and yeast treatment, the goal being the long-term storage, aging and even decontamination of such products, and seems to meet the requirements of the winemakers. Using the principles of dielectric barrier discharge, we power up an atmospheric pressure plasma jet in helium. This plasma is used for treatment of fresh must obtained from white grapes. Our research manuscript is focused on the correlation of plasma parameters (applied voltage, plasma power, reactive species, gas temperature) with the physico-chemical properties of white must and wine (1 and 2 years old), via ultraviolet–visible and infrared spectroscopy, and colorimetry. Two types of white must were plasma treated and studied over time. The 10 W plasma source did not exceed 40 °C during treatment, the must did not suffer during thermal treatment. A higher quantity of RONS was observed during plasma-must exposure, supporting further oxidation processes. The UV-Vis and FTIR spectroscopy revealed the presence of phenols, flavones and sugar in the wine samples. Simultaneous visualization of CIE L*a*b* and RGB in color space charts allows easier understanding of wine changing in color parameters. These experimental results supporting the possible usability of atmospheric pressure plasma for winemaking.

Acoustic characterization of atmospheric-pressure dielectric barrier discharge plasma jets

In this work, we report the acoustic measurements performed on an atmospheric-pressure plasma jet (APPJ) ignited at various electrical conditions, and attempt to describe the origin of plasma-generated sound waves. The working principle of the APPJ source used for this investigation was based on a DC-pulsed dielectric barrier discharge in a helium flow. Our results indicated that the sound is generated in the plasma core in a glass tube between two cylindrical electrodes, rather than in the plasma jet that extends into the open atmosphere. We also explored the electrical conditions at which the sound level is below 85 dBA; that is, still within the safe level recommended by the National Institute for Occupational Safety and Health. Therefore, our findings can be used to advance our basic and applicable knowledge of APPJs.

Study on helium atmospheric pressure plasma jet using collisional-radiative model

The helium (He) non-thermal atmospheric pressure plasma jet (APPJ) source was configured, and the He spectra were measured by applying AC power to the source. A He collisional-radiative (CR) model was developed to investigate the He spectra obtained from the APPJ source. Different atmospheric pressure (AP) processes were evaluated, and the dominant processes among them that contribute to the He spectra were determined. The plasma parameters of the APPJ were determined using the He CR model, and the He spectra were successfully reproduced. The electron density was determined to be ∼2×1012 cm−3 between the electrodes of the APPJ, and ∼9×1011cm−3 outside the quartz tube, for a frequency and bias of an AC voltage source of 5 kHz and 10 kVp.p, respectively. A parametric study was performed to explain the behavior of the electron temperature and electron density of APPJ.

Super-hydrophobic film deposition by an atmospheric-pressure plasma process and its anti-icing characteristics

In this work, the super-hydrophobic (SH) surface was prepared through chemical vapor deposition process by an argon atmospheric pressure plasma jet source with HMDSN (hexamethyldisilazane) as the polymerization precursor. Plasma synthesized organosilicon (SiOxCyHz) thin films with water contact angle over 160° and sliding angle below 5°, were able to be achieved. FTIR and XPS analysis indicates a large number of hydrocarbon compositions were polymerized in the thin films enduing the latter very-low surface free energy. SEM shows the SH films display micro-nanostructure and with high degree of averaged surface roughness 190 nm evaluated by AFM analysis. From experiments under controlled low-temperature and moisture conditions, the prepared SH surface exhibits good anti-icing effects. Significantly prolonging freezing time was achievable on the SH thin films for both static and sliding water droplets. This investigation demonstrates the anti-icing potentials of SH surface prepared through low-cost simple atmospheric-pressure plasma polymerization process.

Polymer etching by atmospheric‐pressure plasma jet and surface micro‐discharge sources: Activation energy analysis and etching directionality

Treatments of polymer films using either a MHz atmospheric pressure plasma jet (APPJ) or an atmospheric pressure surface micro‐discharge (SMD) plasma are investigated. While the typical approach to determine relevant reactive species is to correlate surface effects with gas phase species measurement, this does not capture potential synergistic or other complex effects that may be occurring. Activation energy and directionality of the etching process can characterize what is occurring at the surface for these processes in more detail. The APPJ source shows an apparent activation energy of ∼0.18 eV at 8 mm distance and up to ∼0.34 eV at 16 mm distance for a temperature range of 20–80 °C tested with thin polymer films. The APPJ source shows directional etching at 8 mm distance with less anisotropy the more distance is increased. The SMD source has an apparent activation energy of ∼0.8–0.9 eV at a distance of 3 mm. The SMD also only shows isotropic etching behavior. However the SMD surface chemistry changes significantly to less oxidation with increased temperature while the APPJ source induced modifications remain very similar with temperature change. The lower apparent activation energy of the APPJ‐induced etching reactions as compared with low pressure work (0.5 eV) and observation of line‐of‐sight contribution to etching suggests the involvement of a directional species at closer distances facilitating the etching which falls off with increasing distance. The high activation energy of the SMD suggests that species with less capability for etching is responsible compared to the APPJ and low pressure plasma. The high surface oxidation from low temperature SMD treatments shows that the surface is being oxidized but not sufficiently to reach the desorption step of the etching process.

Non-invasive probe diagnostic method for electron temperature and ion current density in atmospheric pressure plasma jet source

The electrical probe diagnostics are very hard to be applied to atmospheric plasmas due to severe perturbation by the electrical probes. To overcome this, the probe for measuring electron temperature and ion current density is indirectly contacted with an atmospheric jet source. The plasma parameters are obtained by using floating harmonic analysis. The probe is mounted on the quartz tube that surrounds plasma. When a sinusoidal voltage is applied to a probe contacting on a quartz tube, the electrons near the sheath at dielectric tube are collected and the probe current has harmonic components due to probe sheath nonlinearity. From the relation of the harmonic currents and amplitude of the sheath voltage, the electron temperature near the wall can be obtained with collisional sheath model. The electron temperatures and ion current densities measured at the discharge region are in the ranges of 2.7–3.4 eV and 1.7–5.2 mA/cm2 at various flow rates and input powers.

Characterization of a Plasma Jet Produced by Spark Discharges in Argon Air Mixtures at Atmospheric Pressure

A stark difference in the electrical, optical and thermal properties of an atmospheric pressure plasma jet source exploiting spark discharges in a gas stream was reported when argon is used instead of air in the flow. Electrical probe results are discussed together with optical ones in order to investigate the discharge properties and the temporal structure of the different pulses of electrical current. If air-argon mixtures are used as feeding gas for the discharge, a sharp transition from a hot plume to a cold plasma jet is observed when argon content exceeds 90 %. Characteristics of the source are examined from the point of view of their utility as a tool for plasma treatment of materials. In this respect, a 10 % air in argon mixture corresponds to a promising oxidizing condition, as revealed by the pronounced peak in atomic oxygen emission intensity.

The influence of the geometry and electrical characteristics on the formation of the atmospheric pressure plasma jet

An extensive electrical study was performed on a coaxial geometry atmospheric pressure plasma jet source in helium, driven by 30 kHz sine voltage. Two modes of operation were observed, a highly reproducible low-power mode that features the emission of one plasma bullet per voltage period and an erratic high-power mode in which micro-discharges appear around the grounded electrode. The minimum of power transfer efficiency corresponds to the transition between the two modes. Effective capacitance was identified as a varying property influenced by the discharge and the dissipated power. The charge carried by plasma bullets was found to be a small fraction of charge produced in the source irrespective of input power and configuration of the grounded electrode. The biggest part of the produced charge stays localized in the plasma source and below the grounded electrode, in the range 1.2–3.3 nC for ground length of 3–8 mm.

Hybrid Laser-Plasma Micro-Structuring of Fused Silica Based on Surface Reduction by a Low-Temperature Atmospheric Pressure Plasma

In this contribution, we report on a novel hybrid laser-plasma method for material processing applications. This method is based on the combination of both an ArF excimer laser (λ = 193 nm) and a low-temperature atmospheric pressure plasma jet source for the chemical reduction of glass surfaces. Here, a hydrogen-containing plasma gas was applied. Due to the layer of silicon suboxide that is generated in this vein, the absorption of the incoming machining laser beam is significantly increased after 15 minutes of plasma-treatment. Several machining experiments in terms of frontside ablation were performed on fused silica. Here, both pure and plasma-treated surfaces were ablated using single laser pulses with a pulse duration of 20 ns. By introducing the presented hybrid technique, the ablation threshold for micro-structuring was reduced significantly by a factor of 4.6 whereas the peak-to-valley height Rz of the machined area was decreased by a factor of 2.3. Further, back-side ablation using the presented method was considered. By a terminal tempering process, the initial transmission characteristics of fused silica can be reconstituted.

Striation and plasma bullet propagation in an atmospheric pressure plasma jet

An atmospheric pressure plasma jet source driven by pulsed wave of several tens of kilohertz and by sinusoidal wave was designed and characterized. A newly designed jet consists of a sharpened tungsten pin electrode covered with a cone type Teflon layer confined in a Pyrex tube. This structure provides an efficient ignition since the electric field is concentrated on the end of electrode. Using the electrical and optical characterization, the properties of plasma bullet were explored. For the Ar plasma jet driven by a pulsed wave at low duty cycles, the volume, the speed, and the luminosity of the plasma bullet became larger, and the striation behavior was observed.