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In this study, cold atmospheric pressure plasma jet was adopted to glass fibers surface modification with tetraethyl orthosilicate as a precursor. To enhance the interfacial bonding forces of glass fiber reinforced polypropylene (GFRP) composites, SiOx nanoparticles were polymerized on the fiber surfaces. The effect of two factors (the distance between nozzle and fiber (D) and the treatment time (T)) on the interfacial bonding behavior of GFRP composites was studied. The modified fibers and composites properties, including surface topography, chemical composition, wettability and interfacial mechanical properties, were studied comprehensively. The optimal parameters were obtained at D = 17 mm and T = 12 s. Our results indicated that the interlaminar shear strength of GFRP composites was increased by 30.79% compared to control group. Further studies found that plasma treatment introduced larger surface roughness, surface energy and more oxygen-containing functional groups, which was responsible for the interlaminar shear strength improvement. [ABSTRACT FROM AUTHOR]

A dielectric barrier discharge (DBD) in atmospheric pressure air was excited by a high-voltage pulse power supply. Capacitors with different capacitance were connected in the discharge circuit and their effects on discharge power calculation were evaluated. The average power deposited into the discharge were calculated by three different methods: 1) Lissajous figure; 2) product of voltage and current; and 3) watt-hour meter. Further studies showed that the capacitor with 10 nF was suitable for power calculation. At applied voltage of 9 kV, discharge power calculated by three methods were similar (around 25–27 W). However, with the increase of applied voltage, the discharge power obtained by product of voltage and current was far beyond the real value. Lissajous method has proven more appreciable for discharge power calculation in a pulsed plasma at high voltage. This study provides a practical guide for power calculation in a pulsed-driven DBD system. [ABSTRACT FROM AUTHOR]

Three types of gases, pure argon (99.999%), argon with 2% oxygen, and argon with 2% oxygen and 10% nitrogen were used as operating gases of a direct current atmospheric pressure cold plasma jet to inactivate Staphylococcus aureus (S. aureus) suspended in a liquid. The inactivation efficacies for the plasma jets operating in the three gases decrease from Ar/O2(2%) to Ar/O2(2%)/N2(10%) to pure Ar. Optical emission spectroscopy, electron spin resonance spectroscopy, high performance liquid chromatography, and atomic absorption spectrophotometry were employed to identify and monitor the reactive species in the plasma-liquid system for the three operating gases and revealed the presence of O, 1O2, OH, NO, H2O2, O3, and NO3-/NO2- as well as Cu+/Cu2+. The S. aureus inactivation results indicate that atomic oxygen (O) is the key inactivation agent, while other species play a lesser role in the inactivation progress studied here. [ABSTRACT FROM AUTHOR]

Both atmospheric pressure dielectric barrier discharge (AP-DBD) deposition and direct fluorination are effective methods to modify the surface electrical properties of polymer insulation. To investigate the surface charge decay properties of Al 2 O 3 -filled epoxy resin (ER) prepared by AP-DBD and direct fluorination treatments, before and after drying, samples were studied under various treatment parameters. The experimental results show that charge decay rates for AP-DBD and fluorinated samples are more than 90% after 5 days in ambient air. The corresponding bulk and surface resistivity is reduced when the charge decay rate increases. After a longer time, the surface charge on the fluorinated samples decays faster than those on the AP-DBD samples before drying. The hydrophilicity of the fluorinated samples significantly affects the surface charge decay after drying. After 100 days of storage, the decay rates for the fluorinated samples decrease with increased storage time (less than 9% after 100 days) while for AP-DBD treated samples the decay rates exceed 24%. The surface resistivity of the AP-DBD samples is always lower than that of the fluorinated ones. Therefore, for a long storage time, AP-DBD treatment may provide a better solution to the surface charge decay of ER than direct fluorination treatment, after drying. [ABSTRACT FROM AUTHOR]

Long-time partial discharge (PD) is regarded as one of the main reasons for the insulation failure of high-voltage cables. In this work, we report on the application of atmospheric pressure plasma to deposit siloxane film on copper to avoid PDs. The dielectric barrier discharge (DBD) plasma is driven by AC power supply, with tetraethoxysilane (TEOS), argon, and oxygen mixture as the source gas. The effect of oxygen gas flow rate on the thin film surface morphology, chemical composition, and electrical properties is studied systematically. Our results show that the stability of the plasma deteriorated, when the oxygen flow rate exceeded 10 sccm. The addition of oxygen in the source gas induced a high oxidation level of deposited thin film. The chemical composition of thin film was in the form of SiOx ( x = 1.9) with 10 sccm oxygen compared to SiOx ( x = 1.2), when deposited in the absence of oxygen. Additionally, the optimal thin film with good stability was obtained with the surface resistivity 1.1 × 1011 Ω, when deposited in the absence of oxygen. The corresponding relative permittivity of the deposited thin film is 2.9. The simulation results demonstrated that the electric field distortion was weaken after the film deposition, which reduced the probability of PD to occur. [ABSTRACT FROM AUTHOR]

In this paper, an atmospheric-pressure dielectric barrier discharge is used to modify the surface of the epoxy material and enhance the dissipation of surface charge to reduce the accumulation of surface charge. In the experiments, atmospheric-pressure air dielectric barrier discharge is driven by a microsecond pulse generator. Surface properties of epoxy before and after the plasma treatment are characterized by water contact angle, surface potential, and surface/volume conductivity measurements. Atomic force microscope and X-ray photoelectron spectroscopy are used to investigate the changes of the morphology and the chemical composition of the epoxy surface. Experimental results indicate that the surface of epoxy is etched by the plasma and the increase of the surface roughness enhances the surface insulation ability. The O radicals in plasma and the carbonyl groups formed on the surface make the surface charge trap shallower, change the epoxy surface composition then increase the surface conductivity and accelerate surface charge dissipation. When the epoxy is treated for an appropriate time, the epoxy surface insulation performance will be enhanced obviously and the surface charge dissipation will be accelerated. [ABSTRACT FROM PUBLISHER]

In this paper, atmospheric pressure plasma jet was used to deposit SiO x film on aluminum surface and the influence of the substrate temperature on the film properties was studied. The results showed that the substrate temperature increase promoted the precursor decomposition and film growth rate. Si-O-Si bond angle and film composition changes were observed after substrate temperature increased. An excellent insulation property of the deposited film was obtained at a moderate substrate temperature of 300 °C. An excessive increase of the substrate temperature reduced the film growth rate and even led to porous structure. In addition, aging experiments under thermal condition and high electric field duration confirmed that the estimated service life of the film was close to 50 years. This paper provides a universal treatment method for improving nonthermal plasma deposited film properties. • SiO x film structure transition was observed by changing substrate temperature in plasma film deposition process. • The substrate temperature increase promoted the precursor decomposition and film growth rate. • The excellent insulation properties of the film were obtained at a moderate substrate temperature of 300 °C. • The film lift-off voltage and relative dielectric constant rose by more than 180.8 % and 50 %, respectively. • The estimated service life of the film was close to 50 years based on aging experiments. [ABSTRACT FROM AUTHOR]

In recent years, surface dielectric barrier discharge (SDBD) sustained by pulse power supply has been widely investigated due to its high efficiency and fast response. In this paper, in order to obtain the effect of the electrode length, dielectric thickness, and electrode width on the characteristics of SDBD driven by microsecond-pulse generator, experimental investigation on the SDBD actuator using a dielectric barrier of epoxy glass cloth is performed. The experimental results showed that both the current amplitude at the rising edge of the applied voltage and the consumption energy increased with the electrode length. Moreover, dielectric thickness slightly affected the displacement current, while the consumption energy decreased when the dielectric thickness increased. Furthermore, when the electrode width increased, the current at the rising edge of the applied voltage increased, but it would reach the saturation when the electrode width exceeded 3 mm. Both the instantaneous power and the consumption energy increased with the electrode width. The experimental results can provide reference for the optimal design of the SDBD actuator driven by microsecond pulses. [ABSTRACT FROM AUTHOR]

Compared with other non-thermal plasma sources, the atmospheric-pressure plasma jet (APPJ) has advantages on simple structure, low temperatures, strong chemical activities, and convenient handling, all of which have attracted much attention. The power sources play an important role on the characteristics and the applications of the APPJ. In this article, a compact repetitive microsecond-pulse generator is designed for exciting the APPJ in helium and argon. The microsecond-pulse generator can produce repetitive pulses with output voltages of up to 20 kV, pulse width of ~8 ????s, and pulse repetition frequencies (PRFs) of 1 Hz ~2 kHz. Using the designed repetitive microsecond-pulse generator, the characteristics of the APPJ are investigated by measuring the voltages and currents and obtaining images of the discharges. Experimental results show that the microsecond-pulse generator has been successfully used to sustain stable APPJs both in helium and argon. The shape of the output voltage pulses may change as the applied voltage increases. Nevertheless, the output voltages are stable at all PRFs when the applied voltage is fixed. Furthermore, the effects of flow rate, the applied voltage, and the PRF on the He/Ar APPJ are investigated. Results show that it is more likely to generate a He APPJ rather than an Ar APPJ under microsecond-pulse excitation. The length of the plasma plume is slightly affected by the PRF both in the He APPJ and the Ar APPJ. [ABSTRACT FROM PUBLISHER]

In order to compare the characteristics of plasma jets in He and Ar, the plasma jets are driven by a home-made microsecond pulse power, which provides 0–30-kV output voltage with a rise time of 0.5 $\mu $ s and full-width at half-maximum of 4 \mu $ s, and the pulse repetition frequency can be changed from single shot to 5 kHz. The main electrical parameters, such as applied voltage, total discharge current, and jet current, are measured. Results show that the intensity and length of jets become stronger and longer as the voltage increases. The discharge current of He plasma jet is only a few millamperes, whereas Ar plasma is hundreds of millamperes. For both cases, the jet speed is on an order of \sim 10^{4} m/s estimated by the intensified charge coupled device images. The analysis shows that the differences between He and Ar plasma jets are mainly due to the physical and chemical characteristics of Ar and He gases, especially the different ionization energies of particles. In addition, the optical spectrum results show that there are more excited OH radicals and N2 of the second positive system in Ar plasma jet while the He plasma jet contains more excited O and N2+ of the first negative system. [ABSTRACT FROM PUBLISHER]

A plasma jet driven by microsecond pulse was used for polymethylmethacrylate (PMMA) surface modification. In the paper, the effect of different proportions of Ar and CF 4 gas mixture on PMMA modification was studied. After plasma treatment, PMMA samples were immersed in water to accelerate the aging effect. The morphology and elemental composition of the material surface were investigated by atomic force microscopy and X-ray photoelectron spectroscopy. In addition, the mechanism for plasma surface modification has been analyzed. Results showed that plasma treatment introduced hydrophobic groups (i.e. C–F n and C–F) into material surface and increased their surface roughness. In the initial stage of plasma treatment, the contact angle of PMMA decreased and showed a hydrophilic property. After water immersion with different time, the oxygen-containing groups (C O) were gradually displaced by C–F n and C–F and showed a hydrophobic property. The increased roughness and fluoride groups on the PMMA surface were responsible for hydrophobic behavior of PMMA. [ABSTRACT FROM AUTHOR]

In this paper, an atmospheric pressure plasma jet driven by an AC power supply was applied for SiO x film deposition on a metal surface. To improve the adhesion strength between the film and substrate, the processes of plasma etching and annealing were applied. The deposited SiO x film properties, including film thickness, surface morphology, chemical composition and electrical properties, were studied systematically. In addition, the deposited film was used for the metal particle lift-off voltage in a gas-insulated line (GIL) system. Our results showed that the adhesion strength between the film and substrate was 5 times higher in the films subjected to plasma etching and annealing treatment than that in the untreated group. The high oxygen content attained in the SiO x film after the etching and annealing processes was responsible for the adhesion force improvement. The composition changes in the film also increased the relative constant value, which was in good agreement with the metal particle lift-off voltage results. After thermal annealing, the sample showed a 119% improvement in the lift-off voltage compared to that of the bare electrode. • The plasma etching and annealing processes improved the adhesion force between SiO x film and substrate by 5 times; • A rich oxygen contained and randomly oriented SiO x film was obtained after etching and annealing processes; • The SiO x film with a high oxidation degree possesses a high relative dielectric constant value; • The SiO x deposited sample showed a 119% improvement in the lift-off voltage compared to that of the bare electrode. [ABSTRACT FROM AUTHOR]

The mechanisms of eukaryotic cell response to cold plasma are studied. A series of single gene mutants of eukaryotic model organism Saccharomyces cerevisiae are used to compare their sensitivity to plasma treatment with the wild type. We examined 12 mutants in the oxidative stress pathway and the cell cycle pathway, in which 8 are found to be hypersensitive to plasma processing. The mutated genes' roles in the two pathways are analyzed to understand the biological response mechanisms of plasma treatment. The results demonstrate that genes from both pathways are needed for the eukaryotic cells to survive the complex plasma treatment. [ABSTRACT FROM AUTHOR]

In this study, we developed a simple-to-use approach based on an atmospheric pressure plasma jet to synthesize aqueous Au nanoparticles (AuNP). Special attention was paid to the different reaction dynamics and AuNP properties under AC and pulse-power-driven plasma jets (A-Jet and P-Jet, respectively). The morphology of the AuNP, optical emissions, and chemical reactions were analyzed. Further, a copper mesh was placed above the reaction cell to evaluate the role of electrons and neutral species reduction. A visible color change was observed after the A-Jet treatment for 30 s, while it took 3 min for the P-Jet. The A-Jet treatment presented a much higher AuNP growth rate and a smaller AuNP diameter compared with the P-Jet treatment. Further analysis revealed an increase in chemical concentrations (Cl− and H2O2) and liquid conductivity after plasma treatment, with a higher increased amplitude for the A-Jet case. Moreover, the electrons alone had little effect on AuNP generation, while neutral species showed a clear Au+ reduction effect, and a unique coupling effect between both reactions was observed. The different reaction dynamics between the A-Jet and P-Jet were attributed to their different local heating effects and different discharge power during the reaction. [ABSTRACT FROM AUTHOR]