Plasma degradation of trichloroethylene: Process optimization and reaction mechanism analysis

In this study, a multi-pin-to-plate negative glow discharge reactor was employed to degrade the hazardous compound, trichloroethylene (TCE). The response surface methodology (RSM) was applied to examine the influences of various process factors (relative humidity (RH), gas flow rate, and discharge power) on the TCE decomposition process, with regard to the TCE removal efficiency, CO2 and CO selectivities. The variance analysis was used to estimate the significance of the single process factors and their interactions. It has been proved that the discharge power had the utmost influential impact on the TCE removal efficiency, CO2 and CO selectivities, subsequently the gas flow rate, and finally RH. Under the optimal conditions with 20.83% RH, 2 W discharge power and 0.5 L·min–1 gas flow rate, the optimal TCE removal efficiency (86.05%), CO2 selectivity (8.62%), and CO selectivity (15.14%) were achieved. In addition, a possible TCE decomposition pathway was proposed based on the investigation of byproducts identified in the exhaust gas of the NTP reactor. This work paves a way for the control of chlorinated volatile organic compounds.

Studies and Research on Obtaining Multifunctional Thin Films by Magnetron-Assisted PVD Process

The paper aims to obtain thin films of nickel and zinc through the magnetron-assisted spraying process and their characterization from a structural point of view, of electrical, optical properties and corrosion resistance. It was found that as the intensity and discharge power increase, changes occur in the structure and properties of the deposited films.

A half-bridge IGBT drive and protection circuit in dielectric barrier discharge power supply

Purpose This paper aims to improve the general circuit of driving and protection based on insulated gate bipolar transistor (IGBT) in dielectric barrier discharge power supply by designing a novel half-bridge inverter circuit with discrete components. Design/methodology/approach With one SG3524 chip, the structure based on discrete components is used to design the IGBT drive circuit. The driving waveform is isolated and sent out by photo-coupler 6N137. The protection circuit is realized by Hall sensor directly detecting the main circuit current, supplemented by a few components, including diodes, resistors, capacitors and triodes. It improves the reliability of the protection circuit. Findings In the driving circuit, the phase difference of signals from two channels are 180°. Moreover, when the duty cycle is set at 40%, it can ensure sufficient pulse width modulation response time. In the protection circuit, when over-current occurs, an intermittent output signal is automatically sent out. Furthermore, the over-current response time can be controlled independently. The peak voltage can be adjusted continuously from 0 to 30 kV with its frequency from 8 to 25 kHz and the power output up to 150 W. Originality/value The novel circuit of driving and protection makes not only its structure simpler and easier to be realized but also key parameters, such as frequency, the duty cycle and the driving voltage, continuously adjustable. Moreover, the power supply is suitable for other discharges such as corona discharge and jet discharge.

Wettability Increase in Plasma-Treated Agricultural Seeds and Its Relation to Germination Improvement

The literature on plasma-stimulated modification of seed wettability and germination is reviewed and analyzed. The results reported by different authors are scattered, but there is a positive correlation between the change in the water contact angle and the germination improvement. There is hardly any correlation between the germination and the power density used for sustaining gaseous plasma. The wettability, on the other hand, exhibits optimal values at the power density of roughly 1 W cm−3, but the results differ significantly. In fact, a super hydrophilic surface finish was only reported at such moderate power densities. Both the wettability and germination increase with treatment time, but saturate at a certain level, depending on the discharge power. Unlike for most polymers, the hydrophobic recovery does not appear to be a considerable obstacle, so the plasma treatment may be performed well before sowing, which makes the technique applicable in agricultural practice. The scattering of results indicates that the commonly reported parameters such as the type and mode of discharge, the discharge power or power density, the type of gas and its pressure, the treatment time and the type of the seeds, are not decisive parameters governing wettability and germination. Based on the observations of the reviewing authors, conclusions and scientific challenges in this scientific niche are summarized.

Plasma-Catalytic Process of Hydrogen Production from Mixture of Methanol and Water

In the present work the process of hydrogen production was conducted in the plasma-catalytic reactor, the substrates were first treated with plasma and then introduced into the catalyst bed. Plasma was produced by a spark discharge. The discharge power ranged from 15 to 46 W. The catalyst was metallic nickel supported on Al2O3. The catalyst was active from a temperature of 400 °C. The substrate flow rate was 1 mol/h of water and 1 mol/h of methanol. The process generated H2, CO, CO2 and CH4. The gas which formed the greatest amount was H2. Its concentration in the gas was ~60%. The conversion of methanol and the production of hydrogen in the plasma-catalytic reactor were higher than in the plasma and catalytic reactors. The synergy effect of the interaction of two environments, i.e., plasma and the catalyst, was observed. The highest hydrogen production was 1.38 mol/h and the highest methanol conversion was 64%. The increased in the discharge power resulted in increasing methanol conversion and hydrogen production.

Chlorobenzene Removal Using DBD Coupled with CuO/γ-Al2O3 Catalyst

The removal of chlorobenzene using a dielectric barrier discharge (DBD) reactor coupled with CuO/γ-Al2O3 catalysts was investigated in this paper. The coupling of CuO enhanced the chlorobenzene degradation and complete oxidation ability of the DBD reactor, especially under low voltage conditions. The characterization of catalyst was carried out to understand the interaction between catalyst and plasma discharge. The effects of flow rate and discharge power on the degradation of chlorobenzene and the interaction between these parameters were analyzed using the response surface model (RSM). The analysis of variance was applied to evaluate the significance of the independent variables and their interactions. The results show that the interactions between flow rate and discharge power are not negligible for the degradation of chlorobenzene. Moreover, based on the analysis of byproducts, 4-chlorophenol was discriminated as the important intermediate of chlorobenzene degradation, and the speculative decomposition mechanism of chlorobenzene is explored.

Adaptive Mode Selection Strategy for Series-Parallel Hybrid Electric Vehicles Based on Variable Power Reserve

When the series-parallel hybrid electric vehicle exits the pure electric mode, the battery provides power for the drive motor and integrated starter generator (ISG) to drive the vehicle and start the engine. If the battery discharge power is insufficient, the driving power will drop, which will inhibit the vehicle from accelerating and impair drivability. Considering that the mode selection strategy determines the timing of mode switching, this paper proposes an adaptive mode selection strategy based on variable power reserve to allow the vehicle to switch mode considering the battery power limitation. The effectiveness of this strategy is verified by simulation, and its influence on fuel consumption and battery utilization is analyzed. Compared with the mode selection strategy based on logic thresholds at the same initial battery state of charge (SOC), under the high-speed and aggressive US06 cycle, the total driving power drop is reduced by 74.2%, and the over-discharge power of the battery is fully restrained while keep almost the same fuel consumption; under the city FTP cycle, the total driving power drop is reduced 65%, and fuel consumption is reduced while maintaining SOC at a reasonable level.

Physico-chemical properties and wear resistance of nitrided steel 38KhMUA

The influence of regime (temperature, composition of gas mixture and its pressure) and energy characteristics (voltage, current density, specific discharge power) at hydrogen-free-nitriding in a glow discharge (HFNGD) on the structure, phase composition of nitrided layers is investigated. It is shown that due to the combination of regime and energy parameters of HFNGD it is possible to achieve physical and chemical indicators of nitrided layers set by operating conditions. The set of traditionally fixed values of regime parameters (temperature, gas mixture connection, pressure and saturation time) without taking into account energy characteristics (voltage, current density and specific discharge power) significantly reduces the technological capabilities of HFNGD. With controlled regulation of the energy characteristics of HFNGD, a significant reduction in the energy consumption of the nitriding process is achieved. It is established that the energy levels of the main subprocesses differ significantly: the formation of nitrides occurs at low energies, surface sputtering is realized at high voltage values, and nitrogen diffusion occurs at high current densities. In cases where the flow energy is insufficient, either a glow discharge may not occur at all, or at insufficient stress the nitride layer on the surface is not sprayed and it acts as a barrier that prevents the diffusion process into the inner layers of the metal, leading to low physicochemical indicators of nitrided layers. The priority in the formation of one or another phase (, , u, ), the quantitative ratio between them and the required performance properties of the metal, respectively, can be achieved only through an independent combination of energy and regime characteristics of HFNGD.