Non Thermal Plasma

The Electro-Hydro-Dynamic (EHD) interaction induced in atmospheric-pressure air by a surface Dielectric Barrier Discharge (DBD) actuator has been experimentally investigated. Plasma Synthetic Jets Actuators (PSJAs) are DBD actuators able to induce an air stream, perpendicular to the actuator surface. These devices can be used in the aerodynamics field to prevent or induce flow separation, modify the laminar to turbulent transition inside the boundary layer, and stabilize or mix air flows. They can also be used to enhance indirect plasma treatment effects, increasing the reactive species delivery rate onto surfaces and liquids. This can play a major role in plasma processing and chemical kinetics modelling, where only diffusive mechanisms are often considered. This paper reports on the importance that different electrode geometries can have on the performance of different PSJAs. A series of DBD aerodynamic actuators designed to produce perpendicular jets have been fabricated on 2-layer printed circuit boards (PCBs). Linear and annular geometries have been considered, testing different upper electrode distances in the linear case and different diameters in the annular one. AC voltage supplied at 11.5 kV peak and 5 kHz frequency has been used. Lower electrodes were connected to ground and buried in epoxy resin to avoid undesired plasma generation on the lower actuator surface. Voltage and current measurements have been carried out to evaluate the active power delivered to the discharges. Schlieren imaging allowed to visualize the induced jets and gave an estimate of their evolution and geometry. Pitot tube measurements were performed to obtain the PSJAs' velocity profiles and to estimate the mechanical power delivered to the fluid. Optimal values of the inter-electrode distance and diameter have been found in order to maximize jet velocity, mechanical power or efficiency. Annular geometries are found to achieve the best performances.

Aiming at the energy efficient use and valorization of carbon dioxide in the framework of decarbonization studies and hydrogen research, a novel dielectric barrier discharge (DBD) reactor has been designed, constructed and developed. This test rig with water cooled electrodes is capable of a plasma power tunable in a wide range from 20W to 2 kW per unit. The reactor was designed to be ready for catalysts and membrane integration aiming at a broad range plasma conditions and processes, including low to moderate high pressures (0.05–2 bar). In this paper, preliminary studies on the highly endothermic dissociation of CO2, into O2 and CO, in a pure, inert, and noble gas mixture flow are presented. These initial experiments were performed in a geometry with a 3 mm plasma gap in a chamber volume of 40cm3, where the process pressure was varied from few 200 mbar to 1 bar, using pure CO2, and diluted in N2. Initial results confirmed the well-known trade-off between conversion rate (up to 60%...

In the original publication , there was a mistake in Figure as published. The wrong figure was replaced after enhancing the resolution. Corrected Figure appears below. The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.

Atmospheric pressure microplasma jet sources driven by radio‐frequency wave of 13.56 MHz and by low frequency continuous wave of several kHz ac were fabricated and characterized. The source consists of an ac‐driven copper wire (needle) surrounded by dielectric layer that are placed in a glass tube, and a ground plane electrode (pin‐to‐plane electrode configuration). The basic physical and chemical properties of the plasma jet sources, such as optical emission spectrum, gas temperature, and power deposition were investigated. With various geometrical and operational parameters changed, plasma jets showed different discharge characteristics. The geometrical parameters include the length of the pin wire exposed to the plasma, the distance between the pin to the outlet of the glass tube, and the distance between the pin and the plane electrode. The operational parameters include the applied voltage (amplitude and frequency) and the gas flow rate. As an example of biomedical application ...

A newly developed, low cost plasma system that works at atmospheric pressure and operates with both DC or AC high voltage power supplies was presented. This system was tested for its biocidal effect on a wide range of microorganisms in water. Optimal killing parameters such as time, temperature and AC and DC high voltage power levels were tested for bacteria (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus mutans, Bacillus subtilis), yeast (Candida albicans), fungi (Aspergillus niger) and green algae. Results show this system to have a very efficient biocidal effect on most bacteria, algae and fungi in water.

A tunable electron beam generated plasma system has been developed for selective cold plasma treatment of dilute concentrations (1-3,000 ppm range) of hazardous compounds in gaseous waste treatment. This system, referred to as the Tunable Hybrid Plasma (THP), has shown a high degree of efficiency and effectiveness in both laboratory and field tests. Decomposition energy requirements are in the 100 eV per molecule range for treatment of carbon tetrachloride and 10 eV for treatment of trichloroethylene. A cost comparison has been made between the Tunable Hybrid Plasma (THP) technology and three conventional technologies used for emission control of volatile organic compounds (VOCs): granular activated carbon, thermal incineration, and catalytic oxidation. In addition to its environmentally attractive features, THP technology has the potential to be lower cost than other technologies over a range of concentrations and flow rates. Cost projections for the THP system for decomposition of trichloroethylene are around 50 cents/lb for initial concentrations in the few hundred ppm range and flow rates of 5,000 cfm or greater and around $1/lb for 1,000 cfm flow rates. Cost projections for carbon tetrachloride and trichloroethane decomposition using the THP technology are several dollars per pound. The costs for THP treatment are generally significantly lower than costs for use of granular activated carbon and are also quite competitive with costs for thermal incineration and catalytic oxidation.

To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH 2 O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH 2 O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals.

Arc discharges were generated in syngas at very high pressure. Conversion of syngas into C 1 , C 2 , C 3 hydrocarbons was enhanced by very high pressure plasma. Influences of operating pressure and supplying current on this synthesis process were analyzed.

Perfluoroalkyl substances (PFAS) represent one of the most recalcitrant class of compounds of emerging concern and their removal from water is a challenging goal. In this study, we investigated the removal efficiency of three selected PFAS from water, namely, perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA) and pefluorooctanesulfonic acid (PFOS) using a custom-built non-thermal plasma generator. A modified full factorial design (with 2 levels, 3 variables and the central point in which both quadratic terms and interactions between couple of variables were considered) was used to investigate the effect of plasma discharge frequency, distance between the electrodes and water conductivity on treatment efficiency. Then, the plasma treatment running on optimized conditions was used to degrade PFAS at ppb level both individually and in mixture, in ultrapure and groundwater matrices. PFOS 1 ppb exhibited the best degradation reaching complete removal after 30 min of treatment ...

The American Physical Society Investigation of the rates of surface and bulk ROS-generating reactions using indigo dye as an indicator CARLY ANDERSON, DOUGLAS CLARK, DAVID GRAVES, University of California, Berkeley -We present evidence for the existence of two distinct processes that contribute to the generation of reactive oxygen and nitrogen species (RONS) in liquids exposed to cold atmospheric plasma (CAP) in air. At the plasma-liquid interface, there exists a fast surface reaction zone where RONS from the gas phase interact with species in the liquid. RONS can also be produced by "slow" chemical reactions in the bulk liquid, even long after plasma exposure. To separate the effects of these processes, we used indigo dye as an indicator of ROS production; specifically generation of hydroxyl radical. The rate of indigo decolorization while in direct contact with CAP is compared with the expected rate of hydroxyl radical generation at the liquid surface. When added to aqueous solutions after CAP exposure, indigo dye reacts on a time scale consistent with the production of peroxynitrous acid, ONOOH, which is known to decompose to hydroxyl radical below a pH of 6.8. In this study, the CAP used was a air corona discharge plasma run in a positive streamer mode.

dans le cadre du programme de coopération France -Mexique ECOS-ANUIES-SEP-CONACYT M97U01, des projets de recherche CONACYT-UNAM F323-M9211, -400349-5-1843E et -32531-T, UNAM-BID 95-B3-A-DGP-0000-0184, UNAM-DGAPA IN102796 et IN119999, des programmes d'appui PAEP 108315 et 208326, et des programmes de bourses complémentaires nationales DGEP

Erosion of the graphite cathode has been investigated in point-to-plane negative corona discharge in ambient air. Oscillography of discharge current and observation of cathode spot dynamics as well as electron micrography of the cathode surface has been performed. An attempt was made to explain cathode erosion in terms of local electro-explosions caused by pulsed discharge current. Difference of erosion pattern

This study was designed to evaluate the effects of Oxygen and Argon plasma on gutta-percha surfaces. A total of 185 flat smooth gutta-percha surfaces were used. Samples were divided into groups: control: no plasma treatment; Oxygen: treatment with Oxygen plasma for 1 minute; Argon: treatment with Argon plasma for 1 minute. Samples were evaluated topographically by scanning electron microscopy and atomic force microscopy; and chemically by Fourier transform infrared spectroscopy. A goniometer was used to determine the surface free energy and the wettability of the endodontic sealers. Additionally 60 bovine teeth were filled using pellets of guttapercha (control, oxygen and argon plasma) and the sealers. Teeth were evaluated by push-out and microleakage tests. Data were statistically analyzed using specific tests. Argon plasma did not change the surface topography, while Oxygen plasma led to changes. Both treatments chemically modified the gutta-percha surface. Argon and Oxygen plasma increased the surface free energy and favored the wettability of AH Plus and Pulp Canal Sealer EWT. Regarding bond strength analysis, for AH Plus sealer, both plasma treatments on gutta-percha favored the bond strength to dentin. However, for Pulp Canal Sealer, there is no statistically significant influence. For leakage test, dye penetration occurred between sealer and dentin in all groups. In conclusion, Oxygen plasma led to both topographic and chemical changes in the gutta-percha surface, while Argon plasma caused only chemical changes. Both treatments increased the surface free energy, favoring the wettability of AH Plus and Pulp Canal Sealer EWT sealers and influenced positively in the adhesion and leakage.

Back-corona discharge has been successfully applied for decomposition of hydrocarbons. Back-corona discharge is generated in a needle-to-plate reactor, with a corona-counter electrode covered with a perforated mica plate. The results of laboratory experiments show that the back-corona discharge can be more efficient in decomposition of hydrocarbons than positive dc streamer corona discharges.

Non-thermal plasma is a promising technology for high purity nanomaterial synthesis in a fast, flexible and controllable process. Gliding arc discharge, as one of the most efficient non-thermal plasmas, has been widely used in gas treatment but rarely studied for the nanomaterial synthesis. In this study, a comparison study for carbon nanosheets synthesis including toluene dissociation and graphite exfoliation was investigated in a 2D gliding arc reactor at atmospheric pressure. The effects of gas flow rate, precursor concentration and power input on the structures of carbon nanosheets produced through the two synthesis routes were explored and compared. Amorphous carbon nanosheets were produced in both approaches with a few crystalline structures formation in the case of toluene dissociation. The thickness of carbon nanosheets synthesized from graphite exfoliation was less than 3 nm, which was thinner and more uniform than that from toluene dissociation. The flow rate of carrier gas has direct influence on the morphology of carbon nanomaterials in the case of toluene dissociation. Carbon spheres were also produced along with nanosheets when the flow rate decreased from 2 to 0.5 L/min. However, in the case of graphite exfoliation, only carbon nanosheets were observed regardless of the change in flow rate of the carrier gas. The generated chemical species and plasma gas temperatures were measured and estimated for the mechanism study, respectively.

Non-thermal plasma is a promising technology for high purity nanomaterial synthesis in a fast, flexible and controllable process. Gliding arc discharge, as one of the most efficient non-thermal plasmas, has been widely used in gas treatment but rarely studied for the nanomaterial synthesis. In this study, a comparison study for carbon nanosheets synthesis including toluene dissociation and graphite exfoliation was investigated in a 2D gliding arc reactor at atmospheric pressure. The effects of gas flow rate, precursor concentration and power input on the structures of carbon nanosheets produced through the two synthesis routes were explored and compared. Amorphous carbon nanosheets were produced in both approaches with a few crystalline structures formation in the case of toluene dissociation. The thickness of carbon nanosheets synthesized from graphite exfoliation was less than 3 nm, which was thinner and more uniform than that from toluene dissociation. The flow rate of carrier ga...

Olive tree is a typical Mediterranean plant grown in Marmara, Aegean, Mediterranean and South East Anatolian regions of Turkey and important oil sources for Mediterranean countries, fulfilling 90 % of the world olive oil production. Turkey is one of the important producer and stakeholders of olive oils after Spain, Italy, Greece and Tunisia. Cultivated olive cultivars in Turkey represent high genetic diversity, which may result in a standardization problem in terms of olive production and their fatty acid composition because the constituents of the fruit and the composition of its oil mainly depend on several factors such as climate, maturity, index variety, etc. Hence, the present study was designed to investigate the optimal soil characteristics for the favourable oil quality. In the study, the olive oils from South-Eastern region in Turkey according to their fatty acid profiles using gas chromatography of their fatty acid methyl esters were characterized and compared using chemo-...

Effects of non-thermal plasma (NTP) technology on the aroma and phenolic compositions and inactivation of lipoxygenase (LOX) enzyme activity of extra virgin olive oil were investigated for the first time. A short non-thermal plasma treatment with pure argon gas (2 standard liters per minute and an average voltage of 7 kV) was applied for 135 seconds on the olive oil sample. The LOX activity in the NTP treated oil was inhibited up to 42.9% in comparison with untreated oil. Mean values of the peroxides in both samples, expressed in meq oxygen/kg of oil, did not show any statistically significant difference. The values of the antioxidant potentials in the samples proved a mild reduction after NTP treatment. A total of 14 phenols and 31 volatiles were found in both samples with same profile. Although there was a slight difference in the test samples with regard to the concentration of individual phenolic and aroma compounds, this difference was not statistically significant. Therefore, NTP treatment had no statistically significant influence on the antioxidant activity, peroxide value, phenols and volatiles, except LOX activity.

In Europe, inappropriate user behaviours in the operation of wood-burning stoves (WBSs) results in substantial energy losses where fireplaces and conventional stoves are major contributors to undue emissions of health damaging fine particulate matter (PM2.5). The design and adoption of cleaner WBSs are relevant issues to save energy and avoid greenhouse gas (CO2e) emissions. This work compares the operating performance of 3 types of biomass stoves used in Europe in their interaction with dwellings. Field studies were conducted in 24 houses in Portugal and Denmark to analyse wood-burning behaviours and their contribution to residential heating. Laboratory and energy simulations were performed to study their thermal efficiency, PM2.5 emissions and the influence of their usage on the indoor climate. This work shows that the operation of enclosed stoves in uninsulated Iberian homes emit more PM2.5 than the Ecodesign thresholds and cannot provide a stable comfort temperature. Despite red...

Non-thermal plasma treatment by an electrical discharge generated above water was applied to study the destruction of anthraquinonic dye Acid Blue 25 in aqueous solutions. The direct current glow discharge above water sustaining in ambient air was used as a source of non-equilibrium plasma. The effect of operational parameters such as initial dye concentration, discharge current, pH and addition of salts on the substrate degradation was investigated. The highest G

In this work, degradation of the anthraquinonic dye Acid Blue 25 by non-thermal plasma at atmospheric pressure with and without photocatalyst is investigated. Titanium dioxide (TiO2) is used as a photocatalyst. The dye degradation by plasma in the presence of TiO2 is investigated as a function of TiO2 concentration, dye concentration and pH. The degradation rate is higher in acidic solutions with pH of 2 to 4.3, especially at pH 2, and decreases to 0.38 mg L-1 min-1 with the increase of pH from 2 to 5.65. A similar effect is observed in basic media, where a higher degradation rate is found at pH = 10.3. The degradation rate increases in the presence of TiO2 compared to the discharge without photocatalysis. The results show that the degradation of the dye increases in the presence of TiO2 until the catalyst load reaches 0.5 g L-1 after which the suppression of AB25 degradation is observed. The results indicate that the tested advanced oxidation processes are very effective for the de...

The reaction of a waste refrigerant mixture of CFC-12, HCFC-22 and HFC-134a (in an argon/methane bath gas) in a dielectric barrier discharge non-thermal plasma reactor has been studied. The conversion of the major refrigerant, CFC-12, ranged from 59-76 % for an input energy density range of 3-13 kJ/L. The reaction results in the formation of a range of gaseous products as well as non-crosslinked polymers of two distinct fractions.

Abatement of NO using microwave micro-plasma is presented in this paper. The micro-plasma is generated using granular activated carbon (GAC) particles of size (size 2-3mm) in loosely fluidised bed in microwave filed operated at 2.45GHz. A single mode microwave cavity reactor (SMMCR) was constructed and microwave was injected through another slotted waveguide in a sandwiched manner. COMSOL Multiphysics software was used to investigate the microwave electric field and the power density within the SMMCR. Gas mixture of air and 500 ppm NO (in N2) at the flow rate of 2 l/min was passed through a quartz tube centered within SMMCR while the supplied microwave power was very low 10-80 W and NO reduction was greater than 98%. The mass of GAC used for generating the plasma was 5g. When air is mixed with NO (in N2), the efficiency of NOx reduction achieved vary greatly with respect to the supplied microwave energy and behavior has become complex and is not predictable. The gas analyzer (testo 350) was used to measure the gas (NO, NO 2 , CO and O2) concentration and temperature.

Abatement of NO using microwave micro-plasma is presented in this paper. The micro-plasma is generated using granular activated carbon (GAC) particles of size (size 2-3mm) in loosely fluidised bed in microwave filed operated at 2.45GHz. A single mode microwave cavity reactor (SMMCR) was constructed and microwave was injected through another slotted waveguide in a sandwiched manner. COMSOL Multiphysics software was used to investigate the microwave electric field and the power density within the SMMCR. Gas mixture of air and 500 ppm NO (in N2) at the flow rate of 2 l/min was passed through a quartz tube centered within SMMCR while the supplied microwave power was very low 10-80 W and NO reduction was greater than 98%. The mass of GAC used for generating the plasma was 5g. When air is mixed with NO (in N2), the efficiency of NOx reduction achieved vary greatly with respect to the supplied microwave energy and behavior has become complex and is not predictable. The gas analyzer (testo 350) was used to measure the gas (NO, NO 2 , CO and O2) concentration and temperature.

A set of procedures for the design of microwave based non-thermal plasma reactor for the abatement of NOx and SOx from marine exhaust gas is presented in this paper. The design is supported by finite element based analysis developed in COMSOL multi-physics environment. The proposed design suggests that use of rightly chosen slots arrangements for the insertion of microwave energy into the multi-mode cavity can increase the supplied dosage of microwave energy to the gas. Index Terms-Non-thermal plasma, marine diesel exhausts gas abatement, microwave plasma reactors.

Nowadays, the intensity of air pollution, due to the industries and automobiles, has been increasing continuously. Nitrogen oxides (NO X) are one of the most harmful pollutants, which are getting released from both automobile and stationary diesel engines. They essentially need to be removed from the exhaust using after treatment systems. However, the energy required to remove these pollutants is one of the major considerations in selecting the technology for pollutant removal from diesel engine exhaust. A study has been carried out on the non-thermal plasma-based NO X removal technique using various combinations of power supply units and electrode configurations. Three different electrode configurations are tested, in which two are cylindrical electrodes with diameters 3 and 5 mm, and the other one is a square electrode with a diagonal of 5 mm. A comparison is made between the results with two different pulse power supply units, PS-I: high-voltage direct current test set based and PS-II: DC-DC converter based. The square electrode with PS-II has been found to be the optimal combination, which has removed 85% of NO X from the exhaust at an energy density of 55.5 J/L, when the initial NO X concentration in the exhaust is 388 ppm.

The paper analyzes the evolution of scientific production and patenting, main proxies of scientific and technological breakthroughs, concerning non-thermal plasma for biomedical applications in order to detect emerging technological trajectories. New scientific directions of non-thermal plasma in medicine play a critical role because they might generate important innovations that could change the clinical practice. Occurrences of scientific products and patents are retrieved with Boolean queries on SciVerse database after a meticulous procedure to delineate the most promising applications in biomedical sciences. Data are analyzed with two methodological approaches: an exponential model of growth and regression analysis. Results show high rates of scientific growth for applications of nonthermal plasma in disinfection, anticancer treatments, dermatology, whereas for surgery, although values of occurrences are similar to the other research fields, it shows a different trend that after the 2005 is decreasing due to the peculiar application to materials for implantation. Some arguments are discussed at the end of the paper.

The non-equilibrium plasma of diffuse coplanar surface barrier discharge (DCSBD) was tested for decontamination of bacteria Escherichia coli on polymer surfaces. We investigated the optical parameters of DCSBD plasma generated in synthetic air with different relative humidity. Our study was provided to estimate the main plasma components active during the DCSBD plasma degradation of E. coli contamination prepared on polytetrafluoroethylene (PTFE, Teflon) surface, in ambient air at atmospheric pressure. The DCSBD plasma was characterized by means of electrical measurements and optical emission spectroscopy. The inactivation of E. coli bacteria was evaluated by standard microbiological cultivation (CFU plate counting). The experimental results of the germicidal efficiency obtained for short plasma exposure times proved the effectiveness of DCSBD plasma for the polymer surface decontamination.

The non-equilibrium plasma of diffuse coplanar surface barrier discharge (DCSBD) was tested for decontamination of bacteria Escherichia coli on polymer surfaces. We investigated the optical parameters of DCSBD plasma generated in synthetic air with different relative humidity. Our study was provided to estimate the main plasma components active during the DCSBD plasma degradation of E. coli contamination prepared on polytetrafluoroethylene (PTFE, Teflon) surface, in ambient air at atmospheric pressure. The DCSBD plasma was characterized by means of electrical measurements and optical emission spectroscopy. The inactivation of E. coli bacteria was evaluated by standard microbiological cultivation (CFU plate counting). The experimental results of the germicidal efficiency obtained for short plasma exposure times proved the effectiveness of DCSBD plasma for the polymer surface decontamination.

One way to improve the performance of non-thermal plasma (NTP) reactor for volatile organic compound decomposition is by the introduction of ferroelectric materials into the discharge zone of NTP. This paper is a review of the breakthroughs and the current status of the applications of this technology for the abatement of volatile organic compounds (VOCs). It covers the process of energy generation in NTP, VOCs decomposition processes and the effects of critical factors such as type of packed bed materials, dielectric constant, pellet size and shape on the VOCs removal efficiency. Finally the mechanism of VOCs decomposition process was also presented.

The use of CaCO3, FeCl3, and FeOOH as powder sorbents for a plasma‐based hydrogen sulfide removal from biogas mixtures was investigated. No plasma‐enhanced surface reactions were observed during the processing. However, the high surface area provided by the powders led to an increased deposition of atomic sulfur. The dissociation of H2S in dielectric barrier discharges was found to be effective for gas purification purposes, but limited by the backwards reaction. Medium high gas velocities in a nozzle‐like plasma reactor and high retention times in a subsequent expansion vessel thus further improved the desulfurization efficiencies. Furthermore, methane production was observed, whereas the sources could not yet be fully identified.

Carmine (C.I. name is Natural Red 4), a naturally occurring important dye, was subjected to UV radiation in the presence of hydrogen peroxide. The photo-oxidation of the dye was monitored spectrophotometrically. The apparent rate of decoloration was calculated from the observed absorption data and was found to be of first order. A systematic study of the effect of dye concentration as well as H 2 O 2 concentration on the kinetics of dye decoloration was carried out. Additionally, the effect of various additives on the decoloration of this dye was also investigated. Most of the anions tested had an inhibitory effect on the decoloration of the dye, with the most pronounced effect seen with sulfite ion as compared to carbonate, sulphate, nitrate and chloride ions. Examination of the effect of pH showed that the dye could be efficiently decolorized in a basic media. A plausible explanation involving the probable radical initiated mechanism was given to explain the dye decoloration. Lastly, we used HPLC analysis to show that the decoloration of carmine observed during the UV/H 2 O 2 photolysis treatment was in fact due to the degradation of the dye.

An ozone production using pulse voltage driven dielectric barrier discharge (DBD) reactor was investigated experimentally to clarify an influence of a duty factor of applied pulse voltage on ozone yield. A square of 10 kV applied voltage was generated using a pulse modulator. Insulated gate bipolar transistor (IGBT) switches were employed to generate the square pulse with 1 kHz in pulse repetition rate. Duty factor of the pulse voltage was controlled in range from 10 to 80% by timing of a gate signal to the IGBT switches. The output voltages of the power supply were applied to a multipoint electrode type DBD reactor in order to operate at low applied voltage. The ozone yield was obtained to be around 100 g/kWh at several thousands ppm ozone production in pure oxygen circumstance at 5 L/min. gas flow. The ozone yield decreased with increasing ozone concentration and was almost independent of the duty factor of square applied voltage under the present experimental condition. Power loss consumed in the pulse modulator was successfully reduced by decreasing duty factor of the output voltage without decrease of the ozone production.

An ozone production using pulse voltage driven dielectric barrier discharge (DBD) reactor was investigated experimentally to clarify an influence of a duty factor of applied pulse voltage on ozone yield. A square of 10 kV applied voltage was generated using a pulse modulator. Insulated gate bipolar transistor (IGBT) switches were employed to generate the square pulse with 1 kHz in pulse repetition rate. Duty factor of the pulse voltage was controlled in range from 10 to 80% by timing of a gate signal to the IGBT switches. The output voltages of the power supply were applied to a multipoint electrode type DBD reactor in order to operate at low applied voltage. The ozone yield was obtained to be around 100 g/kWh at several thousands ppm ozone production in pure oxygen circumstance at 5 L/min. gas flow. The ozone yield decreased with increasing ozone concentration and was almost independent of the duty factor of square applied voltage under the present experimental condition. Power los...

Voltage-current (V-I) characteristics of nitrogen glow discharges at 10 torr gas pressure were obtained in a wide discharge current range from 10 mA to 250 A using parallel-plane electrodes. A low inductance capacitor of 1.89 μF and a discharge apparatus with co-axial configuration were used to produce a nitrogen glow discharge with high current. The time-dependent glow voltage was obtained accurately by solving the circuit equation using the measured values of the current and breakdown voltage. Damping resistor was employed to control the glow discharge current and was altered from 0.6 to 225 Ω in order to obtain the V-I characteristics in a wide current range. The glow discharge voltage was almost constant until the whole surface of the cathode was covered with glow, i.e., until the discharge current became 3.0 A under our experimental condition. The voltage, however, increased with the current when the glow covered over the cathode. Electron density and temperature in a positive ...

Characteristics of a dielectric barrier discharge were investigated experimentally to clarify an influence of an electrode configuration on ozone synthesis and a microdischarge behavior. Three difference configurations: plane, trench and multipoint were employed as ground electrode. The alumina dielectric barrier coated plane electrode was used as a high-voltage electrode, to which a sinusoidal high-voltage was applied with 10 kHz frequency. Pure oxygen gas was fed into the reactor with gas flow rate of 5 L/ min. The maximum yielding rate increased from 80 to 120 g/kWh by changing an electrode configuration from plane to multipoint, which has 528 number of a right-pyramid shape projection on a 6 cm  22 cm plane electrode. The yielding rate was strongly dependent on a produced ozone concentration in the plane electrode case, whereas slightly depended on the concentration in the multipoint electrode case. The electrode configuration also affected a number of the microdischarges per one applied voltage cycle. The multipoint electrode showed the largest number of microdischarges at same input energy.

Capacity-coupled multi-discharge (CCMD), which is essentially a self-quenching discharge in a manner similar to dielectric barrier discharge (DBD), has recently been developed as an atmospheric pressure plasma source. A coaxial cable is employed as a capacitor to quench the discharge within a short time and controls the energy input into the discharge. A needle-to-plane electrode configuration is used as a discharge gap with 1 mm in gap length. The needle electrode is connected to the quenching capacitor. The discharge is successfully quenched within 30 ns by a 9.35 pF quenching capacitor. The energy into the plasma per one cycle of applied voltage is 0.24 mJ, which is almost two orders of magnitude higher than that of a needle-to-plane DBD (2.5 mJ). Power into the plasma increases stepwise with applied voltage. This stepwise increase agrees with the theoretical prediction.

This study investigated the degradation of a model organic compound, reactive blue (RB-19), in aqueous solution using a needle-plate non-thermal plasma (NTP) reactor, which was operated using three gas atmospheres (Ar, air, O2) at room temperature and atmospheric pressure. The relative discharge and degradation parameters, including the peak to peak applied voltage, power, ozone generation, pH, decolorization rates, energy density and the total organic carbon (TOC) reduction were analyzed to determine the various dye removal efficiencies. The decolorization rate for Ar, air and O2 were 59.9%, 49.6% and 89.8% respectively at the energy density of 100 kJ/L. The best TOC reduction was displayed by Ar with about 8.8% decrease, and 0% with O2 and air atmospheres. This phenomenon could be explained by the formation of OH• and O3 in the Ar and O2 atmospheres, which are responsible for increased mineralization and efficient decolorization. A one-dimension model was developed using software ...

In the past few years, air pollution control has been a priority of the European Union. In this paper, we present a new process specifically designed to treat bitumen fumes from covering plants: this process couples the destruction of the pollutant by activated (radicals and ions) molecules produced by a dielectric barrier discharge (DBD), a nonthermal plasma, and adsorption of converted pollutant molecules on a mineral bed. The process worked at atmospheric pressure and ambient temperature. Bitumen fumes contain volatile organic components (VOCs) and sulfured molecules responsible for the foul smell. Hydrodynamical simulations predicted that active species and the pollutant mix properly in the reactor, favoring plasma treatment. As a result, pollutant molecules were softly oxidized on ketones or alcoholic functions; their S-C bonds were broken by oxidative species, which led to the production of sulfur dioxide, and converted molecules formed aggregates. Plasma treatment also enhanced pollutant retention by mineral filters. Tests performed on half-scale laboratory pilots showed that the process is efficient in decreasing the VOC concentration, and a larger scale prototype is now being tested on a bitumen plant in France.

The chemistry induced by atmospheric pressure DC discharges above a water surface in CO 2 /N 2 /H 2 O mixtures was investigated. The gaseous mixtures studied represent a model prebiotic atmosphere of the Earth. The most remarkable changes in the chemical composition of the treated gas were the decomposition of CO 2 and the production of CO. The concentration of CO increased logarithmically with the increasing input energy density and an increasing initial concentration of CO 2 in the gas. The highest achieved concentration of CO was 4.0 ± 0.6 vol. %. The production of CO was crucial for the synthesis of organic species, since reactions of CO with some reactive species generated in the plasma, e. g. H• or N• radicals, were probably the starting point in this synthesis. The presence of organic species (including the tentative identification of some amino acids) was demonstrated by the analysis of solid and liquid samples by high-performance liquid chromatography, infrared absorption spectroscopy and proton-transfer-reaction mass spectrometry. Formation of organic species in a completely inorganic CO 2 /N 2 /H 2 O atmosphere is a significant finding for the theory of the origins of life.

Processes such as ablation, erosion and corrosion generally create roughness patterns on solid surfaces. Despite the randomness of this phenomenon, some patterns can be described mathematically by studying statistically the mechanisms behind them. This paper reports an experimental study on the temporal evolution of the roughness development of polymer surfaces exposed to argon non-thermal plasma under reduced pressure of 5 mbar and 65 W of applied power. The substrates studied were polypropylene, high density polyethylene, polyamide-6 and poly(ether ether)ketone. The mean roughness data as well as the saturation roughness values showed differences between polyolefin and polymers containing heteroatoms and notably the dependence of the etching on the packing density of the polymer chains. The plasma-etched surfaces were described statistically as self-affine surfaces using scaling law analysis, exhibiting roughness exponents of α ca.0.73 ± 0.2 and growth exponents of β ca. 1.0 ± 0.1. The roughness increases and decreases successively during treatment although presenting a general linear behavior in a non-monotonous way, as a function of time. The models for the shadowing and redistribution of active species can be complemented with the transient crosslinking model of the observed flattening stages.

 A novel double dielectric barrier discharge plasma reactor with a liquid interface has been designed  It is possible to totally convert inulin into 100 % fructose and glucose  No degradation products are generated  Combined analytical results evidenced the acidic attack of the glycosidic bond leading to depolymerization Abstract We report the complete conversion of inulin in gas/liquid media by a dielectric barrier discharge plasma at atmospheric pressure. Depending on the plasma treatment time (from 1 to 30 min) and the chemical nature of the gases (air, oxygen, nitrogen), it was possible to depolymerize inulin into fructo-oligosaccharides with a degree of polymerization inferior to 5 or to achieve a total conversion of inulin into its two monomeric constituents, fructose and glucose in 20 min, without any degradation products. Combined results from liquid chromatography (HPLC), solid state Nuclear Magnetic Resonance (ssNMR) and mass spectroscopy revealed that the breakage of the  1-4-bridged oxygen occurs by an acidic attack, following the oxidation of the polymer. Infrared spectroscopy revealed the oxidation and breakage of the polymer and also adsorption of nitrate species.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.