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In this study, the generation of cold atmospheric plasma jet was investigated in a coaxial double dielectric barrier configuration conjugated with a microsecond voltage pulse generator. The advanced reactor comprised two coaxial dielectric tubes of different diameters with two ring-shaped electrodes covering outside the larger tube. The electrodes were immersed in a liquid dielectric (i.e. transformer oil) in order to isolate them from the ambient air, which completely prevented the direct sparks formation between them within the investigated range of the applied voltage. The He discharge gas was fed to the inner tube while either air, N2, or O2 as a shielding gas was introduced into the gap between the two dielectrics. The result revealed that with these shielding gases, the unwanted abnormal discharge in the inter-dielectric gap was extinguished and the plasma discharge occurred only in the He gas in the inner tube. Consequently, the electrical power delivered to the He discharges maintained at a level of around 1 W with a considerable variation in the applied voltage. Meanwhile, the discharge power of the unshielded jet was almost tripled as the applied voltage was increased from 7 to 10 kV. Interestingly, the cold plasma jet generated by the alternative reactor design in this study, which had the electron density up to 2.5 × 1013 cm−3, consumed relatively less He gas with less restriction on the high voltage range applied. The design also enhanced the possibility to control the plasma chemistry and jet temperature by changing the shielding gas. Therefore, the reactor is capable of producing a cold atmospheric plasma jet for the emerging plasma application such as plasma medicine and bio-applications. [ABSTRACT FROM AUTHOR]

A conventional coplanar-coaxial dielectric barrier discharge is operated with two-ring electrodes exposed to the atmosphere; however, this condition can potentially generate sparks between the electrodes. Here, we showed that sparks between the electrodes were avoided by completely covering the electrodes in the electrical insulation. This new configuration provided a high-level performance in generating a plasma jet in comparison with the configuration with the electrodes exposed to the atmosphere, i.e., it provided a stable discharge and long-plasma plume, reduced discharge power, and increased the range of applied voltage. A short distance between the electrodes and the ground electrode led to an extended jet length and a reduced jet temperature. This is a promising plasma jet source for various applications in that excited species are present in the jet and the emission of NOx and CO is low. [ABSTRACT FROM AUTHOR]

An alternating-current-driven, atmospheric-pressure, non-thermal plasma reactor was applied to the degradation of dye in water. The plasma reactor, made of a porous hollow ceramic tube, was placed underwater and was able to disperse plasmatic gas containing various reactive species into aqueous dye solution as small bubbles through the micropores of the tube. The hydrophobic coating on the surface of the ceramic tube effectively prevented the water from permeating through it. This wastewater treatment system was able immediately to transfer plasmatic gas to aqueous solution across the porous ceramic tube and provide a large gas-liquid interfacial area, allowing efficient dye treatment. So as to simulate real dyeing wastewater, an aqueous solution comprising two different azo dyes was used. The effect of discharge power, treatment time, and flow rate of oxygen used for the creation of plasma was examined. The results suggest that this system may be useful for the treatment of organic wastewater. [ABSTRACT FROM AUTHOR]

Highlights: [•] Atmospheric pressure plasma technique for RuO2 nanomaterials synthesis. [•] Substrate induced morphological variations. [•] Visible light photo-catalysis. [•] Shape dependent catalytic properties. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated the decomposition of ethylene in a continuous flow dielectric-packed bed plasma reactor filled with various packing materials at atmospheric pressure and room temperature. When compared to the case without any packing material, the reactor filled with packing materials remarkably facilitated the plasma-induced decomposition of ethylene in the order of α-alumina>silica>zirconia>glass wool (GW). Under identical condition, the increase in the decomposition efficiency (DE) with increasing the specific energy input was more rapid in the plasma reactor filled with the packing materials than in the blank plasma reactor. In the early stage, almost complete decomposition of ethylene was observed with the α-alumina, but after a certain period of time, the DE decreased with time. Unlike the α-alumina, the other packing materials examined did not show any significant deterioration in the decomposition over time during 10-h operation. After the regeneration of the used packing materials by using the plasma in the presence of oxygen, the original decomposition performance was nearly recovered. The decrease in the BET surface area due to the formation of polymer deposits was observed in the used α-alumina and silica; however the surface area was almost regained by the regeneration. While no other byproducts except carbon oxides and N2O were detected with the α-alumina and silica, methane, acetylene, formaldehyde and N2O were identified in the effluent gas with the zirconia and GW packing materials. [Copyright &y& Elsevier]

A method based on the corona discharge produced by high voltage alternating current (AC) and direct current (DC) over a Pd/γ-Al 2 O 3 catalyst supported on a honeycomb structure monolith was developed to eliminate ethyl acetate (EA) from the air at atmospheric pressure. The characteristics of the AC and DC corona discharge generated inside the honeycomb structure monolith were investigated by varying the humidity, gas hourly space velocity (GHSV), and temperature. The results showed that the DC corona discharge is more stable and easily operated at different operating conditions such as humidity, GHSV, and gas temperature compared to the AC discharge. At a given applied voltage, the EA conversion in the DC honeycomb catalyst discharge is, therefore, higher compared with that in the AC honeycomb catalyst discharge (e.g., 96% of EA conversion compared with approximately 68%, respectively, at 11.2 kV). These new results can open opportunities for wide applications of DC corona discharge combined with honeycomb catalysts to VOC treatment. [Display omitted] • Uniform plasma generation inside honeycomb without significant pressure drop. • Positive DC discharge is more stable and easier to operate than AC discharge. • Ethylacetate removal was as high as 96% in the DC plasma/honeycomb catalyst. • Feasibility of DC plasma-in-honeycomb for practical pollution control applications. [ABSTRACT FROM AUTHOR]

Nitrogen fixation (NF) was investigated in a rotational gliding arc plasma based on various energy inputs, flow rates, and N 2 :O 2 ratios under atmospheric conditions. For practical application, the effect of water content in the feed, self-heating during plasma discharge, prolonged operation, and comparison between plasma and thermal process for N 2 oxidation were also conducted. The comparison results reveal that NF by the gliding arc plasma is superior to the thermal process in terms of NO x yield and energy consumption at low temperatures and atmospheric pressure. Herein, energy input and flow rate are two controlled factors that significantly influence NO x production rate. Simultaneously, O 2 content played a crucial role in determining NO x yield, selectivity of NO/NO 2, and energy consumption. Observations during plasma discharge indicated an initial rise in gas and reactor body temperatures, coinciding with decrease in total NO x formation. Moreover, the presence of water had a negative effect on NO x yield. Accordingly, the optimized conditions for NF by gliding arc plasma for NO x formation was identified at a N 2 to O 2 ratio of 3:2 without water vapor in the feed gas. Furthermore, a 14-h continuous operational test validated the robustness of our reactor configuration, affirming its long-term viability. The study concludes by performing oxidation of the NO x gas followed by dissolution in water, successfully generating nitric acid. These findings underscore the potential of gliding arc plasma for efficient NF processes, offering insights into optimal operational conditions and downstream applications for nitric acid generation. [Display omitted] • Effective N 2 oxidation to form NO x by gliding arc plasma. • Optimized gas feed ratio for the plasma process was N 2 :O 2 = 3: 2. • Water vapor in feed led to a decrease in NO x yield and energy efficiency. • Efficient operation of reactor for long duration with stable NO x generation. • HNO 3 was produced via N 2 fixation. [ABSTRACT FROM AUTHOR]

Abstract The conditions for the deposition of stable superhydrophobic coatings on glass substrates using a dielectric barrier discharge plasma jet with tetramethylsilane (TMS) and 3-aminopropyl(diethoxy)methylsilane (APDMES) as precursors were investigated. The coatings, which were formed under different plasma conditions, were characterized by various methods including atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, static water contact angle (WCA) and sliding angle measurement, and a scratch test. The results presented that superhydrophobic and mechanically stable plasma coatings could be obtained by optimizing the treatment time, applied voltage, gas flow rate into the plasma chamber, and APDMES/TMS ratio. The results indicated that the use of TMS on its own as the coating precursor led to the formation of unstable coatings. However, the mechanical stability increased significantly when APDMES and TMS were used in combination. As a result, a durable coating layer with a WCA of 163° and sliding angle of 3° was achieved for an APDMES/TMS ratio of 1.7. Highlights • Superhydrophobic coatings using non-thermal atmospheric-pressure plasma jet. • Plasma copolymerization of tetramethylsilane and an aminosilane for stable coating. • Maximum water contact angle of 163° with a sliding angle of 3°. [ABSTRACT FROM AUTHOR]

Abstract Non-thermal plasma is getting more popular in industrial applications, mainly treatment of material surfaces. Hydrophobic coatings often suffer mechanical instability and do not function well after abrasion/scratching. In this study, non-thermal plasma jet generated at atmospheric pressure in ambient condition was applied to the hydrophobic treatment of glass surface using two precursors. Tetramethylsilane (TMS) was used to promote hydrophobicity and (3-Aminopropyl)triethoxysilane (APTES) was used to get durable mechanical strength of the coating although it is hydrophilic in character. An alternating current (AC) high voltage (operating frequency: 11.5 kHz) was used to generate plasma jet for producing a coating layer onto the soda-lime glass sample. Water contact angle of 139° and a stable mechanical strength were achieved at an optimal TMS/APTES ratio of 4.8. The coating thickness, strength and water contact angle were varied by changing treatment time, applied voltage, and carrier gas (argon) flow rate. The coating layer were characterized by atomic-force microscopy (AFM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), water contact angle (WCA), scratch test and UV/visible spectroscopy. Highlights • Robust coating on the glass by APPJ conjugated with two precursors • Coating strength depended on the flow rate, voltage, time and TMS/APTES ratio. • The coating exhibited good durability, mechanical strength and thermal stability. [ABSTRACT FROM AUTHOR]

Highlights: [•] Large gas–liquid interfacial area and instant transfer of reactive species to water. [•] Effective decomposition of taste-and-odor compounds and cyanobacteria algae. [•] Good correlation of the decomposition efficiency to the specific energy input. [Copyright &y& Elsevier]

• The methane conversion shows its maximum in terms of particle size. • The concept of microelectrodes explains the existence of maximum conversion. • By adjusting particle size, selectivity can be controlled without catalyst. • In terms of coke formation, non-porous silica particles are favored. • Coke is more produced when large particles are used. A dielectric barrier discharge (DBD) plasma reactor was employed for non-oxidative coupling of methane. The coupling reaction in the DBD plasma bed was conducted near atmospheric pressure and room temperature. In the bed, dielectric materials such as ordered mesoporous silica (KIT-6), sea sand silica, and α-Al 2 O 3 were employed. This non-catalytic reaction system could successfully activate C H bond to produce methyl radicals and light hydrocarbons without additional thermal energy and oxidant molecules. The gap distance between dielectric particles was determined by their sizes, which was experimentally shown. The effects of gap distance were found significant on the conversion and the selectivity. The existence of maximum conversion at a specific gap distance was experimentally observed and could be described successfully by using a newly developed concept of micro-electrodes. Based on the concept, the minimum threshold electric potential difference between the dielectric particles could be successfully estimated, where the conversion was shown to be maximized. Furthermore, it seemed quite possible to control the compositions of ethane, ethylene, and acetylene by properly adjusting the size or the gap distance of particles. [ABSTRACT FROM AUTHOR]

Non-thermal plasma is getting more popular in industrial applications, mainly treatment of material surfaces. Hydrophobic coatings often suffer mechanical instability and do not function well after abrasion/scratching. In this study, non-thermal plasma jet generated at atmospheric pressure in ambient condition was applied to the hydrophobic treatment of glass surface using two precursors. Tetramethylsilane (TMS) was used to promote hydrophobicity and (3-Aminopropyl)triethoxysilane (APTES) was used to get durable mechanical strength of the coating although it is hydrophilic in character. An alternating current (AC) high voltage (operating frequency: 11.5 kHz) was used to generate plasma jet for producing a coating layer onto the soda-lime glass sample. Water contact angle of 139° and a stable mechanical strength were achieved at an optimal TMS/APTES ratio of 4.8. The coating thickness, strength and water contact angle were varied by changing treatment time, applied voltage, and carrier gas (argon) flow rate. The coating layer were characterized by atomic-force microscopy (AFM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), water contact angle (WCA), scratch test and UV/visible spectroscopy. • Robust coating on the glass by APPJ conjugated with two precursors • Coating strength depended on the flow rate, voltage, time and TMS/APTES ratio. • The coating exhibited good durability, mechanical strength and thermal stability. [ABSTRACT FROM AUTHOR]