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This report describes an investigation by experimentation to elucidate atmospheric discharge plasma induced using a 50 kW millimeter-wave beam at 94 GHz. Millimeter-wave discharge plasma is useful for an ultraviolet light source, radioactive material detection, chemical decomposition, and beamed energy propulsion (BEP). The gyrotron used in this study is the "UT-94" with a frequency of 94 GHz and an output power of 100 kW, which was developed at the University of Tokyo specifically for BEP research. The 94 GHz frequency is promising for atmospheric energy beaming because of its low atmospheric attenuation, small beam divergence, and existing utilization track records in the atmosphere. This study experimentally investigated the relationship between the incident beam power density and propagation velocity of an ionization-wave front, which is particularly critical to thrust performance. In addition, the plasma structures were also clarified at 94 GHz and compared with other microwave and millimeter-wave frequencies, such as 28 GHz and those higher than 100 GHz. As a result, finer microscopic structure in the H–k plane was observed than those reported in earlier studies. Furthermore, we found a clear relation between structures and propagation velocities in terms of the electric field concentration of the incoming electromagnetic-waves. [ABSTRACT FROM AUTHOR]

Carbon deposits consisting of vertically oriented multilayer graphene sheets on metallic foils represent an interesting alternative to activated carbon in electrical and electrochemical devices such as super-capacitors because of the superior electrical conductivity of graphene and huge surface–mass ratio. The graphene sheets were deposited on cobalt foils by plasma-enhanced chemical vapor deposition using propane as the carbon precursor. Plasma was sustained by an inductively coupled radiofrequency discharge in the H mode at a power of 500 W and a propane pressure of 17 Pa. The precursor effectively dissociated in plasma conditions and enabled the growth of porous films consisting of multilayer graphene sheets. The deposition rate varied with time and peaked at 100 nm/s. The evolution of surface wettability was determined by the sessile drop method. The untreated substrates were moderately hydrophobic at a water contact angle of about 110°. The contact angle dropped to about 50° after plasma treatment for less than a second and increased monotonously thereafter. The maximal contact angle of 130° appeared at a treatment time of about 30 s. Thereafter, it slowly decreased, with a prolonged deposition time. The evolution of the wettability was explained by surface composition and morphology. A brief treatment with oxygen plasma enabled a super-hydrophilic surface finish of the films consisting of multilayer graphene sheets. [ABSTRACT FROM AUTHOR]

We report on electron spin resonance studies of H atoms stabilized in solid H 2 films at temperature 0.7 K and in a magnetic field of 4.6 T. The H atoms were produced by bombarding H 2 films with 100 eV electrons from a radiofrequency discharge run in the sample cell. We observed a one order of magnitude faster H atom accumulation in the films made of para-H 2 gas with a small ortho-H 2 concentration (0.2% ortho-H 2 ) as compared with those made from normal H 2 gas content (75% ortho-H 2 ). We also studied the influence of ortho-H 2 molecules on spatial diffusion of H atoms in solid H 2 films. The spatial diffusion of H atoms in both normal and para-H 2 films is faster than the diffusion obtained from the measurement of H atom recombination. The rate of spatial diffusion of H atoms in para-H 2 films was slower in comparison with that in the normal H 2 films. We discuss possible explanations of these observations. [ABSTRACT FROM AUTHOR]

An understanding of the degradation mechanism of a microwave discharge cathode is the key to extending the lifetime of microwave ion thruster systems. This study investigates the effect of nozzle contamination by sputtered Ag-polytetrafluoroethylene (PTFE) on microwave discharge cathode performance. The current–voltage characteristics were measured for nominal and contaminated (by PTFE spray with 0.2 µm thick or tape with 0.15 mm thick) cathodes. The contamination thickness and area on the nozzle were varied to investigate the characteristic differences. It was confirmed that the anode voltage increased by 20 V or more in the case of the contaminated cathode. The anode voltage was measured for the sputter-contaminated cathode to evaluate the effect of contamination under more realistic conditions. After 630 h of sputter-contamination operation, it is estimated that sputtered particles were deposited to a thickness of 77 µm at most, and the anode voltage increased by 8 V. The results show that the downstream surface of the nozzle is critical for maintaining cathode performance. The insulating coating formed by the sputtered PTFE may interfere with ion absorption and degrade electron emission capability. A theoretical model based on the extended Brophy model supports these results. This study provides important information for the use of PTFE-based materials around ion thrusters. [ABSTRACT FROM AUTHOR]

In the experiment, plasma–dust clouds were obtained from the substance of the Tsarev meteorite, a simulant of lunar regolith LMS-1D and ilmenite concentrate using a microwave discharge in powder media. For each of the samples, the dynamics of the development of the discharge and the formation of a plasma–dust cloud with subsequent relaxation after the end of the microwave pulse were recorded. From the emission spectra of the plasma and the surface of a solid body, the temperatures of the gas, electrons and surface were determined. A comparison of the phase and elemental composition of the initial samples and samples after exposure to plasma showed that there is no significant change in the composition. However, scanning electron microscopy results clearly indicate spheroidization of the original angular and irregularly shaped particles. The appearance of spherical particles is also observed, the dimensions of which are larger than the linear dimensions of the particles in the original sample. The results obtained indicate the possibility of using such experiments to study chemical and plasma-chemical processes of synthesis and modification of substances under conditions of plasma–dust clouds encountered in space phenomena. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge (DBD) plasma has several applications in different fields. One of these fundamental applications is medical usages, where various methods are employed to improve the plasma treatment process. The combination of different gases is one of the important strategies to improve the performance of plasma in treatment. In this paper, the optimized plasma parameters for one-dimensional radiofrequency discharge produced at low pressures in a helium gas combination is studied. In this research, the optimal combination of H2O and He is identified to attain the highest amount of reactive oxygen species (ROS). Considered mixture are 5, 10, 15 and 20 precent of H2O for one dimensional helium gas discharge. The results show that the parameters of the output plasma are highly dependent on the composition of the input gases. It is found that the greatest concentrations of H+, H+, Hes (excited helium), and OH densities are observed when the H2O percentage was at 10%. Moreover, the density distributions of various species and the temperatures of electrons are numerically calculated during the electrical discharge process. These findings provide useful knowledge on how to optimize plasma parameters for biomedical applications, which may lead to improved treatment results in several therapeutic areas. [ABSTRACT FROM AUTHOR]

Using chromatography, the gas composition in a cold plasma jet, which is a flowing afterglow of a microwave glow discharge at atmospheric pressure, is analyzed. The plasma jet is formed by the interaction of the discharge plasma with atmospheric air behind the outlet of the 6-electrode plasma torch, electrical power to which is supplied from the waveguide microwave (2.45 GHz) plasmatron. An analysis of the gas samples of the jet shows that when plasma-forming argon flows through the microwave discharge, hydrogen and methane are formed behind the discharge region, and the concentration of carbon monoxide increases by 5–6 times. The reactive oxygen species in the cold plasma jet is studied using liquid chromatography of an aqueous solution of isopropyl alcohol after treatment with the plasma jet. It is found that because of plasma treatment, partial oxidation of isopropyl alcohol to acetone occurs. This makes it possible to consider acetone as an indicator of reactive oxygen species (hydroxyl radicals, atomic oxygen and ozone) in a cold plasma jet. [ABSTRACT FROM AUTHOR]

A method for activating water by plasma of an electrodeless torch discharge in a microwave electromagnetic field in argon in an environment of water vapor, at atmospheric pressure, to obtain a pure solution of hydrogen peroxide H2O2 without impurities in distilled water is proposed. It is shown that the main mechanism for the formation of atomic hydrogen H• and hydroxyl HO• radicals in the water decomposition is photolysis under the influence of excimer vacuum ultraviolet radiation of argon plasma. Hydrated electrons can be an additional source of radicals in liquid water when the plasma torch comes into contact with the water surface. Today plasma technologies are widely used to produce activated water containing hydrogen peroxide, to solve environmental problems, to increase productivity in agriculture, and for medical use. [ABSTRACT FROM AUTHOR]

A one-dimensional (1D) fluid model is developed to investigate the effect of multi-frequency excitation consisting of consecutive harmonics on the charge of a single dust grain in a weakly collisional capacitively coupled plasma discharge. The spatial distributions of the electron density, the electrons temperature, and the charged particle flux are obtained and analyzed under the effects of the number of harmonics. It is shown that the number of harmonics considerably affects the discharge properties and the sheath thickness. In order to analyze the charge of an injected dust particle under the effect of different operating parameters, the model takes into account the electron and ion currents, as well as the effect of collisions between ions and neutral atoms. The results showed that as the number of harmonics increases, the particle charge increases in the powered sheath region while it decreases in the grounded sheath due to the electrical asymmetry effect. However, the charge remains constant in the central region where the electron temperature is constant. The present study further shows that the gas pressure and the driving frequency affect the dust charge oppositely, where an increase in pressure leads to a decrease in the dust charge, especially in the sheath regions, while the particle charge negatively increases as the driving frequency increases for all excitation waveforms. [ABSTRACT FROM AUTHOR]

For atmospheric argon RF dielectric barrier discharges, a self-consistent one-dimensional fluid model based on the drift-diffusive approximations of the particles is established to investigate the role of the neutral gas temperature on the discharge process and the plasma characteristics. A finite difference method is used to solve numerically the model, and the numerical results are obtained for the cases that the neutral gas temperature varies from 300 to 600 K. It shows that an increase in the neutral gas temperature causes a decrease in the ionization rate peak and a decrease in the plasma density, but the electric field and the electron temperature do not change very much. Moreover, the discharge mode transition from α mode to α-γ mode occurs because the growing ion flux induces more secondary electron flux, even if the ions entering the sheaths decrease. In addition, the ground state ionization and the ground state excitation are the main collisions in the argon discharges. When metastable atoms are focused on, the three-body quenching is also an important collision progress. [ABSTRACT FROM AUTHOR]

Thermal stability and the kinetics of thermal decomposition of the thermally reduced graphene oxide (TRGO) treated by a pulsed high-frequency discharge in a hydrogen atmosphere have been studied. The modified Hummers method was used for obtaining the initial graphite oxide from graphite powder. Thermal exfoliation of the graphene oxide powder has been done in vacuum conditions with a heating rate of 5–7 degrees per minute to a temperature of 300 °С. TRGO has been treated by pulsed high-frequency discharge in a hydrogen atmosphere for partial graphene hydrogenation (chemical addition of atomic hydrogen) that leads to structural changes in the carbon planes and formation of C–H sp3 bonds. The thermogravimetry analysis measurements of the mass loss have been carried from room temperature to 1000 °C in a nitrogen atmosphere with a nitrogen flow rate of 20 mL/min and different heating rates: 50, 75 100, 125, 150, and 200 K/min, respectively. Kissinger's multiple heating rate method has been used to determine the activation energy for decomposing substances. Activation energies Ea1, Ea2, and Ea3 equal 28, 50, and 148 kJ/mol, respectively, have been compared with the energies of the activation of thermal defunctionalization of multiwalled carbon nanotubes (MWCNTs). The activation energy Ea3 = 148 kJ/mol is close to that of the thermal decomposition of anhydride functional groups in MWCNT. The value of Ea2 = 50 kJ/mol indicates the presence of the keto and hydroxy acid's function groups on TRGO. Activation energy Ea1 = 28 kJ/mol related with all other groups including the lighter C–H bonds that destructed due to dehydrogenation of the TRGO. Obtained experimental results are useful for further proposing the kinetic model of the mechanism of the most probable reaction of TRGO decomposition. [ABSTRACT FROM AUTHOR]

Ammonia have been attractive as one of the alternative fuels for reducing greenhouse gas (GHG) emissions. However, ammonia combustion has lower combustion performance than common hydrocarbon fuels. Furthermore, it may emit nitrous oxide (N 2 O), which is one of the GHGs. This paper presents the experimental investigations of plasma-assisted ammonia combustion (PAAC) using a rod-electrode-type microwave plasma source (MPS) at atmospheric pressure. The equivalence ratios of premixed ammonia/dry air (NH 3 /Air) gas are set below the stoichiometric combustion of NH 3 to reduce toxic NH 3 in the combustion gas. Under the condition of the equivalence ratios, the experiments are focused on reducing the unburned NH 3 and produced N 2 O concentrations in the combustion gas. In the experiments, the unburned NH 3 , nitrogen oxide (NO x) (the sum of nitric oxide (NO) and nitrogen dioxide (NO 2)), and N 2 O concentrations in the combustion gas are investigated in terms of the flow velocity of premixed NH 3 /Air gas inside the rod-electrode-type MPS and the transmission power to the rod-electrode-type MPS. In conclusion, the rod-electrode-type MPS is identified to be useful for PAAC. The NH 3 and N 2 O concentrations in the combustion gas reach approximately 25 and 4 parts per million (ppm), respectively, under the conditions of the equivalence ratio of 1.0, flow velocity of approximately 0.167 m/s, and transmission power of about 84 W. At that time, the NO x concentration is approximately 4300 ppm, and the power transmission efficiency is approximately 68 %. • Plasma-assisted ammonia combustion (PAAC) was conducted using microwave discharge. • The microwave discharge was generated using a rod-electrode-type microwave plasma source (MPS). • The experiments were conducted without a swirler and below the stoichiometric combustion. • The minimum concentrations of NH 3 and N 2 O in the combustion gas reached 25 and 4 ppm. • The rod-electrode-type MPS was identified to be useful for PAAC. [ABSTRACT FROM AUTHOR]

• The relationship between CA3 IEDs and HFOs differs in Septal and Temporal hippocampal slices. • Most differences refer to the timing relationship of HFOs to IEDs. • A juvenile SE changes this relationship in the long term. • Juvenile SE effects differ between Septal and Temporal hippocampal slices. • The IED to HFO relationship provides insights in neuronal network activation patterns. The aim was to investigate the long-term effects of a single episode of immature Status Epilepticus (SE) on the excitability of the septal and temporal hippocampus in vitro , by studying the relationship between interictal-like epileptiform discharges (IEDs) and high-frequency oscillations (HFOs; Ripples, Rs and Fast Ripples, FRs). A pentylenetetrazol-induced Status Epilepticus-(SE)-like generalized seizure was induced at postnatal day 20 in 22 male and female juvenile rats, sacrificed >40 days later to prepare hippocampal slices. Spontaneous IEDs induced by Mg2+-free ACSF were recorded from the CA3 area of temporal (T) or septal (S) slices. Recordings were band-pass filtered off-line revealing Rs and FRs and a series of measurements were conducted, with mean values compared with those obtained from age-matched controls (CTRs). In CTR S (vs T) slices, we recorded longer R & FR durations, a longer HFO-IED temporal overlap, higher FR peak power and more frequent FR initiation preceding IEDs (% events). Post-SE, in T slices all types of events duration (IED, R, FR) and the time lag between their onsets (R-IED, FR-IED, R-FR) increased, while FR/R peak power decreased; in S slices, the IED 1st population spike and the FR amplitudes, the R and FR peak power and the (percent) events where Rs or FRs preceded IEDs all decreased. The CA3 IED-HFO relationship offers insights to the septal-to-temporal synchronization patterns; its post-juvenile-SE changes indicate permanent modifications in the septotemporal excitability gradient. Moreover, these findings are in line to region-specific regulation of various currents post-SE, as reported in literature. [ABSTRACT FROM AUTHOR]

In recent years, interest in striation phenomena in radio frequency (rf) discharges has risen due to the availability of new experimental data and the implementation of new computational models. Depending on the conditions, different mechanisms of discharge striations are realized. These are the ionization instability, the instability due to the electron attachment to electronegative gases, or the instability due to thermoelectric transport. Although the first two mechanisms were modeled quite extensively in recent years, the understanding of the influence of the Dufour effect originating from plasma density gradients on the stability of radio frequency discharges in long tubes remains poor. In this paper, the influence of this mechanism on the longitudinal striations of radio frequency discharge is presented using a one-dimensional model of argon discharge driven with rf excitation under intermediate pressure conditions of 0.5 Torr. It is found that striation formation is sensitive to the value of the thermoelectric heat transport coefficient in the low electron temperature range. The critical value of this coefficient necessary for the instability onset is derived using the linear stability analysis. [ABSTRACT FROM AUTHOR]

The filamentation dynamics of a nitrogen pulsed microwave discharge generated at the antinode of a standing electromagnetic wave at a pressure of 100 torr has been numerically simulated. The results of the dynamics of the main plasma parameters, such as the concentration of charged and excited species, gas temperature, and vibrational temperature of nitrogen, are presented. [ABSTRACT FROM AUTHOR]

The paper is dedicated to the numerical study of the dependence of plasma antenna resonance wavelengths on pressure. The study was carried out by simulating a RF capacitively coupled plasma with the Comsol Multiphysics software in one- dimensional formulation. Based on the calculated electric current in the plasma, the directional pattern and axial distribution of the electromagnetic field were found by solving Maxwell's equations in a 2D formulation. The results showed that one of the advantages of plasma antennas is the transmission of waves at significantly longer wavelengths compared to metal antennas of similar geometry. [ABSTRACT FROM AUTHOR]

A microwave discharge in high-velocity (150–250 m/s) air flows induced on a half-wave vibrator is studied. A cw magnetron microwave generator with a frequency of 2.45 GHz and an output power of up to 5 kW was used for initiation of the microwave discharge. The high-speed video imaging was used for studying the discharge structure, determining the diameter and length of the plasma channel as a function of flow velocity and pressure. Electron concentration and temperature, along with characteristic gas temperature, were determined based on the optical spectra. The possibility of using this microwave discharge for ignition of hydrocarbon–air mixtures in combustion chambers of ramjet engines is proved experimentally. [ABSTRACT FROM AUTHOR]

Energy storage system play a crucial role in safeguarding the reliability and steady voltage supply within microgrids. While batteries are the prevalent choice for energy storage in such applications, their limitation in handling high‐frequency discharging and charging necessitates the incorporation of high‐energy density and high‐power density storage devices to enhance power quality, maintain power balance, and reduce fluctuations. In this study, we introduce a hybrid energy storage system (HESS) solution, combining a battery and a supercapacitor, to address intermittent power supply challenges. The effective management of this HESS is pivotal for constant DC voltage and sustaining microgrid stability. To achieve this, we propose an innovative control strategy called the Adaptive Filter‐Based Method (AFBM) for DC microgrid operation, which prioritizes stable and smooth performance while addressing safety and degradation concerns related to the storage devices. Our control strategy determines the distribution of charging and discharging currents for each storage device within the DC microgrid based on their state of charge. We conducted simulations in MATLAB/Simulink, comparing the proposed AFBM method with the conventional filter‐based approach using identical configurations, parameters, and operational modes. The results demonstrate the superior performance of our proposed system, showcasing improved voltage stability, more equitable load distribution, and efficient charging and discharging of storage devices compared to the traditional method. This research contributes to the advancement of microgrid energy storage solutions, enhancing their reliability and performance. [ABSTRACT FROM AUTHOR]

A fully kinetic 2D axisymmetric Particle-in-Cell (PIC) model is used to examine the effects of background facility pressure on the plasma transport and propulsive efficiency of magnetic nozzles. Simulations are performed for a low-power (150 W class) cathode-less radio-frequency (RF) plasma thruster, operating with xenon, between background pressures up to 1 0 − 2 Pa and average electron discharge temperatures of 4–16 eV. When the electron temperature within the near-plume region reaches 8 eV, a decisive reduction in performance occurs: at 1 0 − 2 Pa, in-plume power losses surpass 25% of the discharge energy flux. Given that the ionisation energy for Xe is 12 eV, the 8 eV threshold indicates that a consistent percentage of electrons has energy enough to trigger ionisation. On the other hand, when the temperature is below such threshold, the primary collisions are charge-exchange and inelastic ion scattering, and the power loss remains less than 10%. It is established that losses in the considered thruster are significant if the facility pressure is greater than 1 0 − 3 Pa, at absorbed powers larger than 130 W. At the nominal 150 W, this results in a 15% thrust reduction. When facility pressure is taken into consideration over ideal vacuum simulations, numerical error is reduced to < 30% when compared to experimental thrust measurements at 1 0 − 3 Pa. • Investigation of facility effects on cathode-less RF thruster performance. • Particle-in-Cell (PIC) simulation of magnetic nozzle expansion into background gas. • Up to 15% thrust reduction at 150 W beyond 1 0 − 3 Pa. • Electron inelastic collisions can cause up to 70% of total in-plume power losses. • Experimental results/setup should therefore take into account facility pressure. [ABSTRACT FROM AUTHOR]

The results of experimental studies on the formation and subsequent evolution of extended (l = 300 mm) and thin-walled (Δr ≈ 10 mm) tubular (2r ≈ 110 mm) plasma in a weak longitudinal magnetic field (B = 175 G) without the use of a thermionic cathode are presented. The cylindrical chamber in which the tubular plasma was formed was pumped with high purity argon (99.998%) at an average velocity of about 1 m/s at a pressure of P = 10–3–10–2 Torr. Two methods of creating seed electrons initiating the development of ionization avalanches were used. The difference inherent to these methods has been established in the dynamics of breakdown, completing in the formation of a tubular discharge. In the first of them, a pulsed discharge preceding the high voltage supply of the main discharge created gas preionization in a small area around the sectioned cathodes. In the second method, seed electrons were created in the entire working area of the discharge chamber by an RF discharge with a frequency of 85 kHz and duration of about 1 s. High-speed shooting with a 4-frame ICCD camera allowed us to establish the dynamics of tubular discharge formation at all its stages. Measurements of the longitudinal and radial discharge current were carried out. The results we obtained showed the possibility of spatial isolation of an extended tubular plasma from the close located metal wall of the discharge chamber by using a weak longitudinal magnetic field. [ABSTRACT FROM AUTHOR]

The influence of current activation by the breakdown of the electric pulse on changes in the surface morphology and emission characteristics of a field emission (FE) cathode made based on carbon films obtained by deposition in a microwave gas discharge plasma is studied. The current activation of these films is carried out by applying microsecond voltage pulses until an electrical breakdown occurred. It is shown that during the activation, the morphology of the film surface in the breakdown region changes with the formation of a microsized emitting structure, which significantly improves the FE characteristics of the cathodes based on carbon films. [ABSTRACT FROM AUTHOR]

The effect of irradiation with a pulsed electron beam on the diffusion of titanium in the polycrystalline Zr-1 wt.% Nb alloy is studied using high-frequency glow discharge optical emission spectrometry. The depth distribution profiles of titanium concentration in the Zr-1 wt.% Nb alloy after isothermal diffusion annealing and annealing under surface irradiation with a pulsed electron beam are determined. It is shown that under simultaneous exposure to temperature and irradiation with a pulsed electron beam, an increase in the coefficient and a decrease in the activation energy of grain boundary diffusion are observed in the near-surface layer of the alloy. [ABSTRACT FROM AUTHOR]

The properties of an inductive RF discharge placed in a longitudinal external magnetic field with an induction of less than 70 G at frequencies of 2, 4, and 13.56 MHz are studied. The dependences of the region of existence of the discharge, the efficiency of the RF power input and the structure of the RF magnetic field on the external magnetic field induction are studied experimentally. The experimental results are compared with calculations based on a previously developed electromagnetic discharge model. It is shown that the local maximum of the plasma density observed at weak magnetic fields is associated with the resonant excitation of waves in the plasma source. The excited wave is close to a transverse helicon at a frequency of 2 MHz, and its properties approach the Trivelpiece–Gould wave at a frequency of 13.56 MHz,. [ABSTRACT FROM AUTHOR]

In this study, a microwave discharge electrodeless lamp (MDEL) photo-degradation system coupled with anatase TiO 2 (P25) was constructed to improve the selective degradation of NH 3 to N 2. The MDEL system can generate abundant reactive oxygen species (ROS) with ultraviolet radiation at 185 nm and 254 nm during gas phase reaction. The species and content of ROS generated in the reaction system were determined by oxidation extraction spectrophotometry, and the effects of residence time, temperature, and relative humidity on the production of reactive oxygen species were investigated. In addition, the removal efficiency under different conditions such as initial ammonia concentration, relative humidity and residence time was explored. It was found that the removal rate could reach 83% when the initial ammonia concentration was 100 ppm, relative humidity was 55% and gas residence time was 5.16 s. The high-energy ultraviolet at 185 nm from MDEL could break NH 3 molecules in advance and produced a large amount of ·NH 2. Besides, NH 3 was converted to N 2 by generating large amounts of ROS, reducing NO x and nitrate generation. Our work presents a novel approach to construct a photocatalytic system for high efficiency degradation of NH 3. [Display omitted] • A novel integrated photocatalytic system combining microwave discharge electrodeless lamp (MDEL) and P25 is constructed to improve selective photodegradation of NH 3. • The highest degradation efficiency of NH 3 can be performed at 100 ppm initial concentration, 55% relative humidity, and 5.16 s gas residence time. • NH 3 can be mainly converted to N 2 with lower NOx and nitrate side-products under MDEL irradiation with anatase TiO 2 as photocatalyst. [ABSTRACT FROM AUTHOR]

Ignition of an ethylene-fueled cavity in Mach-2 flow was performed using nanosecond-pulsed high-frequency discharges (NPHFDs) over a range of pulse repetition frequencies (PRF = 1.5–300 kHz). The energy deposition rate and duration were controlled to be commensurate with the temporal and spatial fluctuations of velocity and fuel concentration within a cavity-based flame holder to enhance the ignition process. Comparison to a traditional capacitive discharge (CD) on an equal-energy basis showed that high-PRF NPHFD operation significantly broadened the ignition envelope: while the CD ignited near-stoichiometric mixtures only (equivalence ratio, Φ = 1.09) the NPHFD operating at PRF = 300 kHz resulted in ignition with Φ = 0.82–1.46. At lean conditions, the NPHFD could achieve comparable cavity ignition times with 5-times lower energy than the CD. Parametric exploration of NPHFD ignition showed that variation of both PRF and number of pulses (N) for the NPHFD were the most significant factors controlling ignition probability (P ig) and ignition time (t ig). PRF>5 kHz was required to achieve cavity ignition, which was the threshold for synergy between pulses to produce an ignition kernel. Higher PRF resulted in more pulse synergy within a burst of pulses, and ultimately higher P ig. These results are similar to those from previous studies of ignition in subsonic flow and correlate well with length/time scales of a fluid volume passing through the inter-electrode gap region. Increased N, which is equivalent to longer discharge duration and higher total energy, increased P ig for 5 kHz50 kHz. Finally, when significant heat release did not occur within 2-3 cavity cycling times after energy deposition, the cavity was far less likely to ignite. The implication is that multiple parameters (i.e., minimum ignition energy, minimum ignition power, t ig , and characteristic flow cycling time) must be simultaneously considered when developing an ignition method in a representative environment. [ABSTRACT FROM AUTHOR]

Microwave discharge electrodeless lamp (MDEL) is a novel ultraviolet (UV) light source. Synergistic disinfection using UV light emitted by MDEL (MWUV) coupled with ozone (O 3) at an ultra-low dose was investigated. Escherichia coli and Bacillus subtilis were deactivated more effectively by MWUV/O 3 than by either MWUV or O 3 alone. MWUV/O 3 treatment using an O 3 concentration of 0.4 mg/L gave an E. coli inactivation rate of 5.52 log. The photoreactivation degree and rate of E. coli were lower after inactivation by MWUV/O 3 treatment than after MWUV treatment alone. The maximum photoreactivation rates after the MWUV/O 3 and MWUV treatments were 2.90% and 16.08%, respectively. MWUV/O 3 disinfection also inhibited dark resurrection of E. coli and gave a maximum dark resurrection rate of 0.0036%. Electron paramagnetic resonance spectroscopy indicated that more hydroxyl radicals were generated during MWUV/O 3 treatment. Scanning electron microscopy and laser confocal scanning microscopy observations indicated that O 3 played a key role in breaking down the cell structure. MWUV/O 3 treatment gave a good disinfection effect on fecal coliform bacteria in actual domestic wastewater. The results indicated that inactivation of bacteria can be more effectively achieved by MWUV treatment with O 3. [Display omitted] • Inactivation of bacteria by MWUV can be enhanced by an ultra-low concentration O 3. • MWUV/O 3 inhibited the photoreactivation and dark resurrection of bacteria. • MWUV/O 3 generated more HO·and accelerated the cell structure destruction. • MWUV/O 3 has a good disinfection effect on fecal coliform in actual wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • H 2 S decomposition is conducted through microwave discharge-catalysis (MDC). • Iron phase transformation is an essential cause to graphitization of bio-char. • The modified bio-chars by graphitization improve the discharge performance. • H 2 S conversion with the method reaches 97.4% and remains at 83.2% after two-hour test. Direct decomposition of hydrogen sulfide (H 2 S) can be used to obtain high-purity hydrogen, thereby avoiding the waste of hydrogen resources by traditional Claus process. Microwave-induced discharge with spherical bio-char for H 2 S decomposition is proposed. The bio-char was treated by graphitization modification in presence of microwave heating and iron additive. The influences of graphitization parameters including iron loading and microwave irradiation time on the bio-char graphitization degree were studied. Subsequently, the modified bio-char was applied to induce microwave discharge, and the effects of graphitization parameters on discharge performance were discussed. Lastly, the attention was paid to investigate catalytic effect of microwave-induced discharge with the modified bio-char for H 2 S decomposition. The results showed the best graphitization degree of bio-char was achieved at iron loading of 6 mmol/g and microwave irradiation time of 60 min. The improvement of bio-char graphitization degree enhanced discharge intensity, thus promoting bed temperature. Microwave discharge exhibited a favorable catalytic effect on H 2 S decomposition, with initial and ending conversions at 97.4% and 83.2% in a two-hour test, respectively, because of synergistic effect of microwave discharge effect, microwave thermal effect and catalytic activity of the modified bio-char. [ABSTRACT FROM AUTHOR]

Microwave discharge electrodeless ultraviolet (MWUV) lamp is a novel type of ultraviolet equipment that utilizes microwave excited plasma to emit ultraviolet light. It offers the advantages of stable light intensity and an extended lifespan. Currently, MWUV has been extensively investigated for pollutant degradation, adsorbent regeneration, and bacterial inactivation. Research has demonstrated that MWUV exhibits remarkable efficacy in degrading norfloxacin, ciprofloxacin, dimethoate, etc ... Moreover, it enables adsorbent regeneration through microwave thermal release and stimulates electrodeless lamps to generate ultraviolet light, thereby reducing environmental pollution. By utilizing the non-thermal effect of microwaves on bacteria which disrupts their structure, MWUV enhances bacterial inactivation via ultraviolet light exposure. The MWUV can be integrated with various processes, such as photocatalytic systems, photo-Fenton, or photoelectric-Fenton systems, through different configurations including microwave oven reactor, exogenous microwave supply reactor, closed chamber reactor, and complete ultraviolet reactor. These systems have been found to produce abundant reactive oxygen species like ·OH, ·O, and ·OH 2. The presence of microwaves promotes free radicals production while lowering the activation energy required for contaminants degradation. Notably, even without microwaves present in the MWUV system, MWUV still exhibit superior photocatalytic performance compared to low-pressure mercury lamps for pollutant degradation. This review provides a detailed introduction to the luminescence mechanisms and structures of MWUV reactors for producing ultraviolet light, as well as their current applications. [Display omitted] • MWUV lamp generates plasma to emit ultraviolet light by microwave excitation. • A variety of MWUV reactors are constructed in collaboration with various oxidation processes. • The participation of microwave promotes the production of more reactive oxygen species. • MWUV enhances the regeneration effect of adsorbent and inactivation effect of bacterial. [ABSTRACT FROM AUTHOR]