Search

Aramid is widely recognized for its effectiveness as a matrix in high-performance composite materials. However, the inert nature of its surface necessitates plasma pretreatment for proper resin immersion. With a particular focus on interactions involving O radicals, this study employs Vacuum Ultra-Violet Photolysis Reactive-species Supply to investigate the interaction mechanisms between aramid and plasma reactive species. The water contact angle serves as an indicator of the degree of surface reactions, demonstrating a clear correlation between its reduction and the concentration of O radicals. Analysis using ATR-FTIR and XPS revealed the depletion of amide groups and the formation of hydroxyl groups during the treatment process. Through reactive molecular dynamics simulations, we identified the specific reaction sites of the amide groups on aramid and quantified the variations in typical reaction products. We also summarized the reaction pathways and confirmed the generation of polar structures, such as N-OH. This study offers valuable theoretical insights for the surface modification of inert polymers and contributes to advancements in industrial plasma technology. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effect of various O 2 concentrations, from 20% to 90%, in nitrogen–oxygen ( N 2 / O 2 ) mixtures on the characteristics of secondary streamers. As oxygen molecules have different molecular characteristics from nitrogen molecules in terms of ionisation threshold and electron attachment property, streamer discharges generated under various nitrogen–oxygen ratios may exhibit differing characteristics such as electron density, electric field, and radical formation. We focused on the changes in these parameters in secondary streamers using simulations. Simulations were first performed under the same conditions as those in previous experiments to compare the results of the ozone production, discharge current, and discharge emission characteristics. To compare the ozone production characteristics, simulated O radicals–the precursor of ozone–were used in the simulation for simplicity. This comparison showed that, although the absolute values of each parameter were different, the simulation exhibited a similar trend in the case of the experimentally obtained oxygen concentration dependence. After the validity of the simulation was verified to some extent via a comparison with the experiment, the results obtained from the simulation were analysed in detail. The results showed that, although the electric field strength in the secondary streamer did not change much as the oxygen concentration increased, the decrease rate of the electron density was greatly accelerated by the electron attachment reaction of oxygen. As a result, many of the electrons had already dissipate during the development of the primary streamer, and few electrons remained when the secondary streamer was formed. This effect suggests that the ratio of the amount of O radicals produced in the primary streamer to that produced in the secondary streamer changes as the oxygen concentration changes. [ABSTRACT FROM AUTHOR]

This study evaluates the individual effects of electron‐impact ionization, attachment, and photoionization on streamer propagation to provide a deeper understanding of the streamer propagation mechanism and useful knowledge to obtain the best set of input data for verification and validation studies. The results show that streamers with higher electron‐impact ionization rates have higher propagation velocities and lower electric fields, while those with higher attachment rates have slower propagation velocities and higher electric fields. Streamers with higher photoionization rates have lower electric fields at the head, but the velocity remains largely unaffected. The effects of different rates of ionization, attachment, and photoionization have been analyzed using an analytical solution called the diameter‐speed relation. [ABSTRACT FROM AUTHOR]

In this paper, we measured the electrical potential distribution of surface dielectric barrier discharges (SDBD) caused by alternating voltage in synthetic air and nitrogen using the Pockels effect. It was shown that different potential distributions of filament thickness and length are generated in synthetic air and nitrogen. A filament analysis based on mathematical morphology was performed to quantify the geometric characteristics of the filaments produced in each gas atmosphere. The results show that the discharge filament thickness and the entropy in the filament direction depend on the oxygen ratio and the magnitude of the applied voltage. [ABSTRACT FROM AUTHOR]

The electric field induced second harmonic generation (E-FISH) technique has been widely utilized for the electric field measurement of atmospheric-pressure nonthermal plasmas. However, the measurement accuracy has not been quantified. Further, the E-FISH signal generation that is necessary to the evaluation of the measurement accuracy has been formulated only for the probe laser beam focused by a spherical lens and not for the cylindrical lens. Here, the E-FISH method utilizing the focusing cylindrical lens was studied for accurate one-dimensional (1D) electric field measurement of the primary-to-secondary transition phase of a single-filament positive streamer discharge generated in atmospheric-pressure air. A combination of numerical analysis and the E-FISH signal measurement was used to establish the radial distribution of the electric field vectors and the accompanying measurement accuracy. The E-FISH methodology captured a distinct evolution in the 1D electric field varying over timescales of ∼ 1  ns and length scales of 100  µ m. At the instant when the primary streamer arrived at the cathode, the electric field at 3 mm above the cathode surface was found to be as high as 225 Td, while the field at 10 mm above the cathode surface was as low as 5 Td. At the final stage of the primary-to-secondary transition phase completed in 3 ns from the primary streamer arrival at the cathode, the electric field at 3 mm above the cathode was found to be lower than that observed at 10 mm from the cathode; this finding is consistent with predictions made based on a previous model describing the initiation of the secondary streamer discharge and previously published electron density measurement. [ABSTRACT FROM AUTHOR]

In order to improve the energy efficiency in the dilute trichloroethylene (TCE) removal by the nonthermal plasma process, the barrier discharge reactor was studied experimentally. It is investigated by combining it with catalyst of manganese dioxide at the downstream of the barrier discharge reactor. Decomposition efficiency by the barrier discharge reactor was about 83% at the gas flow rate 2 L/min, where the dilute TCE concentration is 250 ppm. Decomposition efficiency with passing through manganese dioxide was improved about 99% at the specific energy of 40 J/L. However, other by-products including ozone and oxidation by-products such as DCAC and TCAA were detected by the gas chromatograph mass spectrometry or the Fourier transform infrared spectroscope measurement. DCAC is generated at the plasma reactor, but TCAA is generated at catalyst during ozone decomposition. C[O.sub.x] yield increased about twice with passing through catalyst in the Direct Process. Nitric oxides such as NO, N[O.sub.2], and [N.sub.2]O did not generate so much in this barrier discharge process. The dielectric barrier discharge process combined with manganese dioxide is considered as a very desirable way to improve the energy efficiency. Index Terms--Barrier discharge, manganese dioxide (Mn[O.sub.2]), trichloroethylene (TCE).

Negatively corona-charged 50-[micro]m-thick polypropylene (PP) film is measured using laser-induced pressure pulse (LIPP) and thermally stimulated current (TSC) in order to study the charge storage mechanism in the PP film. The LIPP can reveal the space-charge distribution in the depth direction of the PP films and the TSC can be used to measure the energetic depth of the charge trap. The LIPP shows that negative charge is deposited on the charged surface of the sample. Almost all surface charges are removed by soaking the sample in ethanol. However, about 5% of the surface charge is injected into the sample up to a depth of about 7 [micro]m from the surface. The injected charge is not removed by the dip-in-ethanol method because the ethanol does not penetrate into the sample. The injection of the surface charge increases with corona-charging temperature. Besides the negative charge injection, the injection of positive charge from the opposite surface is also observed when the sample is charged at higher than 60 [degrees]C. In addition, negative bulk charge is formed when the sample is charged at higher than 80 [degrees]C. The LIPP profile is compared with the TSC spectrum. It is shown that the space charge observed using LIPP disappears when the temperature of the sample exceeds 80 [degrees]C. However, TSC is observed at even higher than 80 [degrees]C. This indicates that the TSC is observed even after the disappearance of the space charge measured using LIPP. Index Terms--Corona charging, laser-induced pressure pulse (LIPP), polypropylene (PP) film, thermally stimulated current (TSC).

Sputtering enables uniform and clean deposition over a large area, which is an issue with exfoliation and chemical vapor deposition methods. On the other hand, the process of physical vapor deposition (PVD) film formation has not yet been clarified. We prepared several samples from the sub-monolayer region, and performed Raman spectroscopy, X-ray photon spectroscopy and high-angle annular dark-field scanning transmission electron microscopy. From these results, the internal stresses inherent to PVD films, the bonding states specific to sub-monolayers, and the unique film structure and the grain formation process of PVD films were discussed from the perspective of sub-monolayers. As a conclusion, we found that it is important to suppress the formation of sub-monolayers on the substrate to completely form the first layer. [ABSTRACT FROM AUTHOR]