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We report the two-photon absorption laser-induced fluorescence rotational spectrum of the CO B 1Σ+ ← X 1Σ+ Hopfield–Birge system (v′ = 0, v″ = 0) Q-branch in an ∼4850 K, atmospheric pressure plasma torch plume at thermal equilibrium in both the quenching-dominated (low laser intensity) and photoionization-dominated (high laser intensity) regimes. We provide a detailed analysis of the photophysics in these two regimes using a rate equation approach and propose modeling considerations for them as well. In the experimental spectra, distinct rotational transitions up to J″ = 83 are observed, allowing analysis over a very large range of rotational states. Evidence of predissociation is observed for J′ ≥ 64 and is likely due to the interaction with the D′1Σ+ electronic state, which has been proposed in the literature but never observed in the v′ = 0 state. The line positions of higher rotational states show disagreement with line positions calculated from molecular constants in the available literature, suggesting the need for modifications to the constants, which are reported here. A shift in the B 1Σ+ ← X 1Σ+ absorption spectrum toward higher two-photon energy as a result of the second-order Stark shift was observed in the photoionization-dominated spectrum, and the second-order Stark shift cross section was estimated to be 7 ± 3 × 10−18 cm2. The mean photoionization cross section of the excited upper state was inferred by comparing the line broadening of the two spectra and was estimated to be 11 ± 7 × 10−18 cm2. In addition, weak J′-dependent variations of the photoionization cross section were observed and are reported here. [ABSTRACT FROM AUTHOR]

This study explores the effects of chamber pressure on the electrical and thermodynamic characteristics of a low-pressure thermal plasma jet. The investigation focuses on current–voltage characteristics, arc voltage fluctuations, plasma jet temperature, electron density, and velocity within the range of 100–500 A arc current, at chamber pressures of 100 Pa, 1 kPa, and 3 kPa. Spectral analysis of the arc voltage reveals the presence of distinct frequencies, including restrike, Helmholtz, and acoustic modes, which exhibit varying behavior under different chamber pressure conditions. Restrike frequency shows an increase with decreasing chamber pressure, while Helmholtz frequency remains unaffected, and the power density of the acoustic frequency diminishes, eventually disappearing from the spectrum. The transition of the plasma jet from a continuum regime to a frozen state with decreasing chamber pressure is observed along with its shock structures. Optical emission spectroscopy is utilized to map the excitation temperature and electron density profile along the jet axis, demonstrating that the jet temperature and density peaks at the compression zone. Furthermore, Mach probe measurements of the plasma jet velocity at different axial locations, under various chamber pressure conditions, illustrate that the plasma jet maintains a supersonic state, regardless of chamber pressure. However, after the formation of a Mach disk, the jet velocity becomes subsonic. The highest velocity is achieved at 100 Pa chamber pressure, reaching Mach 2.9 at 50 mm from the anode exit. This research enhances our understanding of thermal plasma jets under low-pressure conditions, contributing to the advancement of knowledge in their applications across various domains. [ABSTRACT FROM AUTHOR]

An atmospheric-pressure microwave plasma torch is employed to generate hydrogen by injecting methanol aerosols into the near afterglow region of a nitrogen microwave plasma. Two types of reaction chambers are proposed to study the influence of different boundary conditions of reaction chambers on hydrogen production by comparison. Fourier transformation infrared spectrometer and gas chromatography are used to measure and determine the hydrogen production rate, energy efficiency, and hydrogen yield. Also, the effects of conditions of methanol injection and discharge parameters on methanol decomposition are investigated, respectively. It is found that the active species originated from collision with the excited and ionized N2 in the high gas temperature in the plasma discharge plays an important role in the conversion of methanol to hydrogen. The gas flow pattern in the reaction chamber is closely related to boundary conditions and significantly affects the reaction time of methanol in it, which is analyzed with the software of computational fluid dynamics. The achievements of hydrogen production in our work are as follows: production rate up to 921 l/h, energy yield up to 371 l/kWh, and hydrogen yield up to 70%, respectively. Furthermore, the reaction mechanism is discussed in detail with respect to the formation of outlet products. [ABSTRACT FROM AUTHOR]

The ablation behavior of (Hf 0.25 Zr 0.25 Ti 0.25 Ta 0.25)C was investigated using a plasma flame gun over a wide temperature range of 2070–2600℃. The structural transformation during ablation and the effect of temperature on the failure mechanism were discussed. Results showed a sharp increase in mass and linear ablation rates from 0.23 mg·cm−2·s−1 and 4.6 μm·s−1 at 2070℃ to 4.6 mg·cm−2·s−1 and 37 μm·s−1 at 2600℃. This variation was attributed to the temperature's impact on on the microstructure and composition of the oxide layer. During ablation, Hf/Zr-rich oxycarbides preferentially nucleated within the amorphous Hf-Zr-Ti-Ta-C-O layer, leading to phase separation of the oxide layer. With increasing ablation temperature, the filler and binder oxides with low melting point (e.g., (Hf,Zr)TiO 4 , TaZr 2.75 O 8) were rapidly consumed. The skeleton oxides (e.g., (Hf,Zr)O 2) failed to bond and peeled off. The transiently formed (Hf,Zr,Ti,Ta)O x layer was repeatedly destroyed and reconstructed, resulting in the continuous damage and eventual failure of the matrix. • Carbides experience a structural transition from amorphous to crystalline oxycarbides during the initial stage of ablation. • Phase separation occurs in the oxide and the oxycarbide layer. • The failure behavior of high-entropy carbides is primarily determined by the consumption of low-melting-point oxides. [ABSTRACT FROM AUTHOR]

This work focuses on the antimycotic effects of the plasma gun as a potential tool for the treatment of superficial infections. Candida glabrata was chosen as a model microorganism. The preliminary tests have been done on the agar plates to establish the basic plasma parameters. To render this research more appropriate to the real application, more complex inoculation substrates, pork skin and 3D‐printed models of the dog ear canal have been used. The results of this work confirm the high efficiency of cold plasma in the inhibition of yeasts on different surfaces and will lead to further experiments. [ABSTRACT FROM AUTHOR]

A proof-of-concept study of the utilization of a single mass spectrometer for qualitative molecular analysis as well as for quantitative metal determination is described. This was performed with an argon microwave plasma as the ion source coupled to an ion trap mass spectrometer. A microwave induced plasma with tuneable power and gas flow rate was loaded with dried nebulized sample solutions. The commercially available plasma torch was slightly modified to allow the introduction of the sample in different regions of the plasma. Using soft settings, organic compounds introduced in the plasma plume could be detected as protonated molecular ions. Under harsher conditions, elemental analysis was demonstrated for several metals. Lead could be determined with a limit of detection of 150 nM. Minor on-the-fly adjustments of the power, flow rate and sampling distance allowed a mild fragmentation of organic compounds. Ionization differences observed were rationalized by emission spectroscopy, and excitation and rotational temperatures were determined. Simultaneous determination of elemental and molecular information was demonstrated for a rubidium–crown-ether complex. The maximum argon gas consumption for these tasks was below 2 L min−1 and the maximal power used was 90 W. [ABSTRACT FROM AUTHOR]

Pyrolysis of methane is a promising, new, greenhouse gas‐free production method of hydrogen. Here, we present optical emission spectra of a microwave plasma torch operated in an argon–methane mixture. Detailed spatial resolution is achieved by means of Abel inversion. The emission spectra are dominated by dicarbon Swan bands and black body radiation from carbon nanoparticles. Both spectral features are utilized to estimate the gas temperature. In the center of the plasma, gas temperatures of up to 4300 K are reached with large gradients (500 Kmm‐1) in the radial direction. The thermal equilibrium chemistry and the kinetics of methane pyrolysis are analyzed to explain the observed coupling between the local gas temperature and the local emission. [ABSTRACT FROM AUTHOR]

This paper presents a detailed review of the plasma gasification process for waste disposal. Due to Shifting economies and consumerism culture, ample change can be seen across the globe in the form of rapid industrialisation and burgeoning urbanisation, which results in a massive increase in waste generation. Plasma gasification technology is an emerging solution for processing a wide range of waste making it a highly sustainable, efficient, and ecologically sound process. This literature review discusses the feasibility of the plasma gasification method and its superiority over other conventional waste disposal techniques. A comprehensive analysis of different methods of plasma generation for gasification is done in this literature review. The review paper presents a detailed coverup of the entire process of plasma gasification and post-processes. The article discusses the notable advancement, current scenario, and possibilities in plasma gasification methodology in terms of the design of plasma torch, modelling of gasifiers, generation of syngas, and power production. It provides an overview of advanced simulation tools helpful in the analysis of the Waste-to-Energy (WtE) process. This literature review aims to provide an overview of the recent advances in plasma gasification, highlighting the technical aspects, environmental benefits, and economic viability of the technology. It also reviews the latest research and developments in plasma gasification and discusses the challenges and limitations of the technology, as well as the future prospects and potential applications. • Plasma gasification methodology for waste treatment is discussed in detail. • Prominent thermal and non-thermal practices are discussed and compared in this literature review. • Selective use of plasma gas for enhanced efficiency and optimised gas yield/composition. • Hybrid systems offer versatility in processing diverse feedstocks and can achieve higher energy efficiencies. • Plasma-catalysis approach with NTP shows desirable syngas yield. [ABSTRACT FROM AUTHOR]

Higher operating temperatures for gas turbine engines require highly durable thermal barrier coatings (TBCs) with improved insulation properties. A suspension plasma spray process (SPS) had been developed for the deposition of columnar-structured TBCs. SPS columnar TBCs are normally achieved at a short standoff distance (50.0 mm–75.0 mm), which is not practical when coating complex-shaped engine hardware since the plasma torch may collide with the components being sprayed. Therefore, it is critical to develop SPS columnar TBCs at longer standoff distances. In this work, a commercially available pressure-based suspension delivery system was used to deliver the suspension to the plasma jet, and a high-enthalpy TriplexPro-210 plasma torch was used for the SPS coating deposition. Suspension injection pressure was optimized to maximize the number of droplets injected into the hot plasma core and achieving the best particle-melting states and deposition efficiency. The highest deposition efficiency of 51% was achieved at 0.34 MPa injection pressure with a suspension flow rate of 31.0 g/min. With the optimized process parameters, 1000 μm thick columnar-structured SPS 8 wt% Y2O3-stabilized ZrO2 (8YSZ) TBCs were successfully developed at a standoff distance of 100.0 mm. The SPS TBCs have a columnar width between 100 μm and 300 μm with a porosity of ~22%. Furnace cycling tests at 1125 °C showed the SPS columnar TBCs had an average life of 1012 cycles, which is ~2.5 times that of reference air-plasma-sprayed dense vertically cracked TBCs with the same coating thickness. The superior durability of the SPS columnar TBCs can be attributed to the high-strain-tolerant microstructure. SEM cross-section characterization indicated the failure of the SPS TBCs occurred at the ceramic top coat and thermally grown oxide (TGO) interface. [ABSTRACT FROM AUTHOR]

Transparent conductive oxide (TCO) films are widely used as electrodes in photovoltaic devices, such as perovskite solar cells and heterojunction solar cells. However, in the conventional physical vapor deposition process, there may be ion bombardment damage to the underlayer coatings, and high deposition temperature also have an adverse effect on perovskite and amorphous silicon layers during TCO deposition. Herein, reactive plasma deposition was effectively utilized for cerium-doped indium oxide (ICO) film as an ultra-transparent electrode. The effects of plasma gun current and the oxygen ratio on the optical and electrical properties, and also on the structure of the ICO films, were investigated. With an industry-scale reactive plasma deposition tool, an outcome of 140-nm ICO film can be achieved within 50 s, which represents a good throughput with the average growth rate of 2.8 nm/s. When the working current was 165 A and the oxygen ratio was 12%, the average transmittance of ICO films reached the highest value (93.09%) in the wavelength range of 400–1200 nm. The average transmittance in the visible wavelength range was 94.23%. The peak transmittance was up to 99.67% at 515 nm, and the corresponding resistivity was 4.68 × 10−4 Ω cm. [ABSTRACT FROM AUTHOR]

The results of preliminary experiments on measuring the spatial asymmetry of plasma flows in the GOL-NB device using movable Mach probe are presented and the diagnostics used is described. In the experiments, the high-field sections were mounted in the configuration with solenoidal magnetic field. The dynamics of plasma flows was recorded which was expected in the trap: the plasma flowed from the plasma gun along the magnetic field, accumulated in the GOL-NB central trap, and then after the plasma gun was switched off, flowed out from the central trap in two directions. At time of transition from the stage of plasma accumulation to the stage of its decay, the direction of plasma flow in the input high-field section was inverted. The balance of particles in the central trap is discussed. Experiments have shown that this technique can be used for studying the effects of improving plasma confinement after switching to the multiple-mirror configuration of high-field sections, in which, according to theory, under optimal conditions, a flow of b-ackscattered particles should arise, which will return them from the multiple-mirror sections to the confinement zone. [ABSTRACT FROM AUTHOR]

Plasma technology, relatively new in the fields of biomedicine, agriculture, and ecology, is the subject of intensive research as a prospective means of decontamination of various microorganisms (bacteria, viruses, and fungi). The objectives of the present study were to follow the effect of cold atmospheric plasma (CAP) treatment on in vitro grown plum plants (Prunus domestica L. 'Kyustendilska sinya' cv.) and the possibility of eradicating or inactivating plum pox virus (PPV) causing Sharka disease by CAP. The source tree is naturally co-infected by PPV (both M and D strains). In the experiments, two different plasma sources were used. First, a surface-wave-sustained Argon plasma torch and second, an underwater diaphragm discharge. For the treatments, nodal segments (10 mm in length) from in vitro cultured plum plants with or without one leaf were prepared. Apical shoots from treated plants (PPV-positive and negative clones as well non-treated controls) were cultivated in vitro for four passages. Then they were rooted and acclimatized to ex vitro conditions, and their virus status was observed periodically for more than 3 years after treatment for the appearance of Sharka symptoms. All plants, acclimatized to ex vitro conditions, were tested for PPV by immune capture–reverse transcription–polymerase chain reaction (IC-RT-PCR). As a first step in understanding the plasma treatment of living plants, a plasma treatment variant causing no damage must be established; this has been done in our previous works. Treatment of plants by plasma with parameters that have been carefully selected leads to better development than the non-treated plants. In the treated in vitro plants, no significant differences were found in the number and length of shoots compared to the control plantlets. In ex vitro acclimated plants, greater stem length was reported, but no differences in leaf number were observed. No significant differences in growth were recorded between the control and plants that were treated twice or three times. At this stage, 3 years after ex vitro cultivation in a greenhouse, Sharka symptoms were not registered on treated in vitro negative PPV plants, and the virus was not detected by IC-RT-PCR. Very mild symptoms were showing in CAP-treated PPV-positive plants. Development of typical Sharka symptoms on non-treated controls were observed. [ABSTRACT FROM AUTHOR]

The stepped-nozzle arc plasma torch (SNAPT) is a promising arc source due to the advantages of high stability and high energy density, but the micro-time scale discharge characteristics have not yet been adequately investigated. In this study, a SNAPT was designed and studied, in order to investigate the effects of discharge current, gas flow rate, and nozzle morphology on the discharge characteristics. The results show that the volt-ampere characteristics of the SNAPT have an increasing curve when the gas flow rate is greater than 4 Nm3/h, and a decreasing curve when the gas flow rate is 3 Nm3/h. This result is related to the position of the arc root, and an arc constriction phenomenon occurs at high current and low gas flow rate. The thermal efficiency of the SNAPT decreases with the increasing current and decreasing gas flow rate, ranging from 69.6 to 82.3% within the experimental parameters. The optical emission spectroscopy results show that there are many active particles inside the plasma. The experimental parameters of the heavy particle temperature of 4851.5 to 9189.3 K and the electron temperature of 7846.9 to 10185.6 K both correspond to the Boltzmann distribution and are close to the local thermodynamic equilibrium state. Comparative experimental results show that the cylindrical-nozzle has the decreasing volt-ampere characteristics and higher voltages, but has large voltage fluctuations and poor stability compared with the stepped-nozzle. The results of the study are of guiding significance for design, selection of operating parameters, and application scenarios for this type of plasma torch. [ABSTRACT FROM AUTHOR]

To investigate the influences of Cr2AlC mass fraction and supersonic plasma spraying process on the microstructure and mechanical properties of Cr2AlC reinforced 410 stainless steel composite coatings, the coatings containing different mass fractions of Cr2AlC were prepared and investigated. The composite coating exhibited low porosity and high adhesion strength. The addition of Cr2AlC significantly enhanced the hardness of the composite coatings through particle strengthening. However, when the mass fraction of Cr2AlC was 20%, the aggregation of Cr2AlC resulted in a strong decrease in the coating preparation efficiency, as well as a decline in adhesion strength. In the supersonic plasma spraying process, the Ar flow rate mainly influenced the flight velocity of the particles, while the H2 flow rate and the current mainly affected the temperature of the plasma torch. Consequently, all of them influenced the melting degree of particles and the quality of the coating. The lowest porosity and the highest hardness and adhesion strength could be obtained when the Ar flow rate is 125 L/min, the H2 flow rate is 25 L/min, and the current is 385 A. [ABSTRACT FROM AUTHOR]

The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater treatment (WWT) sewage sludge through plasma gasification. Effective syngas production hinges on precise equipment design which, in turn, depends on the detailed feedstock used for characterization. Key components of plasma gasification include the plasma torch, reactor, heat exchanger, scrubber, and cyclone, enabling the generation of inert slag for landfill disposal and to ensure clean syngas. Designing these components entails considerations of sludge composition, calorific power, thermal conductivity, ash diameter, and fusibility properties, among other parameters. Accordingly, this work entails the development of an experimental setup for the plasma gasification of sewage sludge, taking into account a comprehensive sludge characterization. The experimental findings reveal that domestic WWT sewage sludge with 40% humidity exhibits a low thermal conductivity of approximately 0.392 W/mK and a calorific value of LHV = 20.78 MJ/kg. Also, the relatively low ash content (17%) renders this raw material advantageous for plasma gasification processes. The integration of a detailed sludge characterization into the equipment design lays the foundation for efficient syngas production. This study aims to contribute to advancing sustainable waste-to-energy technologies, namely plasma gasification, by leveraging sewage sludge as a valuable resource for syngas production. [ABSTRACT FROM AUTHOR]

For low costs, numerical simulation is an effective method to reveal the internal mechanisms inside a thermal plasma torch. Various simulation models for studying the inside or outside characteristics of thermal plasma torches have been built and discussed. However, to reveal the inside mechanisms of thermal plasma torches under various working conditions to support the materials processing, more attention should be paid to building precise models of laminar plasma torches. Thus, based on the user-defined function (UDF) and user-defined scalar (UDS) of ANSYS Fluent software, the assumptions, governing equations, boundary conditions, and solving method were discussed in detail, and a corresponding numerical model of a homemade laminar plasma torch was first built. For verifying the effectiveness of the proposed numerical model and studying the influence of the gas components on the arc characteristics, the working conditions and experimental setups were introduced in sequence. Finally, the numerical and experimental results of the homemade laminar plasma torch were obtained and discussed in detail. The study results show that: ① The axial temperature of the plasma torch could be divided into three sections along the axis: peak temperature area (10 mm < x < 20 mm), stable temperature area (20 mm < x < 62 mm) and decrease temperature area (62 mm < x < 95 mm). Under the same input conditions, when pure argon gas was used, the peak temperature at the outlet was reached at approximately 7590 K, while for pure nitrogen and 50%Ar + 50%N2, the corresponding peak temperatures were 6785 K and 7402.2 K, respectively. ② The axial velocity of pure nitrogen is much higher than that of pure argon and 50%Ar + 50%N2, while that of pure argon and 50%Ar + 50%N2 has little difference. In addition, when nitrogen gas was used, the peak velocity at the outlet reached 185 m/s, whereas, for argon gas and 50%Ar + 50%N2, the corresponding peak velocities were 146 m/s and 169 m/s, respectively. ③ The simulated arc voltage trends under different working conditions are well in accordance with the experimental arc voltage trends. [ABSTRACT FROM AUTHOR]

Non-thermal atmospheric-pressure plasma (NTAPP) has been widely studied for clinical applications, e.g., disinfection, wound healing, cancer therapy, hemostasis, and bone regeneration. It is being revealed that the physical and chemical actions of plasma have enabled these clinical applications. Based on our previous report regarding plasma-stimulated bone regeneration, this study focused on Achilles tendon repair by NTAPP. This is the first study to reveal that exposure to NTAPP can accelerate Achilles tendon repair using a well-established Achilles tendon injury rat model. Histological evaluation using the Stoll's and histological scores showed a significant improvement at 2 and 4 weeks, with type I collagen content being substantial at the early time point of 2 weeks post-surgery. Notably, the replacement of type III collagen with type I collagen occurred more frequently in the plasma-treated groups at the early stage of repair. Tensile strength test results showed that the maximum breaking strength in the plasma-treated group at two weeks was significantly higher than that in the untreated group. Overall, our results indicate that a single event of NTAPP treatment during the surgery can contribute to an early recovery of an injured tendon. [ABSTRACT FROM AUTHOR]

Microwave plasma torch (MPT) has the advantages of low power consumption, convenient operation, simple structure, etc. It can be used with mass spectrometer for rapid analysis of elements. Inductively coupled plasma mass spectrometer (ICP-MS) has many advantages, such as high sensitivity and wide range of analyzed elements, but its high gas consumption and power consumption of ion source make the detection and analysis cost high. In order to effectively reduce the cost of mass spectrometry for the detection and analysis of alkali metal elements, this study reported a self-made low power-consuming microwave plasma torch time-of-flight mass spectrometer (MPT-TOF MS), including a three-cone system consisting of an ion source, a sampling cone, an interception cone, a super-interceptor cone, an ion transport lens set, a time-of-flight mass analyzer, a sample injection device, and a data acquisition system. The effects of five experimental factors, namely, maintenance gas flow rate, carrier gas flow rate, super-interception cone voltage, MPT torch flame position and microwave power, on the detection of alkali metal elements were investigated. The performance of the instrument was systematically investigated, covering the linear range, mass resolution, and isotopic accuracy of measurement. The results showed that the MPT-TOF MS has the advantages of low gas consumption (800 mL/min for argon maintenance gas, 400 mL/min for argon carrier gas, and 2 000 mL/min for nitrogen drying gas), low power consumption of the ion source (100 W), and long-time stable operation when working, and the linear range of the measurement of this device covers five orders of magnitude with high mass resolution. The detection limits of lithium, sodium, potassium, rubidium and cesium are 0.49, 3.05, 1.31, 0.74, 0.34 μg/L, respectively, which are better than the results of ICP-MS. The instrument was used for the rapid detection of lithium, sodium, potassium, rubidium and cesium alkali metal elements in the salt lake. Our study showed that the MPT-TOF-MS instrument can be used as an alternative to the elemental detection of ICP-MS, and can be further developed into an on-line analytical method. [ABSTRACT FROM AUTHOR]

Plasma technology has emerged as a very helpful tool in a variety of sectors, notably metallurgy. Innovators and scientists are focused on the problem of finding a more ecologically friendly way of extracting titanium and iron metal from natural ilmenite concentrate for industrial applications. A direct current (DC) plasma torch operating at atmospheric pressure is used in this study to describe a decarbonization process for reducing an ilmenite concentrate. The plasma gases employed in this torch are CO2 and CH4. The molar ratio of the gases may be crucial for achieving a satisfactory reduction of the ilmenite concentrate. As a result, two molar ratios for CO2/CH4 have been chosen: 1:1 and 2:1. During torch operation, a thin layer of graphite is formed on the cathode to establish a protective barrier, prolonging the cathode's life. The material was analyzed using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The output gases were analyzed using mass spectrometry (MS). In addition, a thermodynamic analysis was performed to predict the development of thermodynamically stable phases. An economic assessment (including capital expenditures (CAPEX) and operating expenditures (OPEX)) and a carbon balance were developed with the feasibility of the piloting in mind. [ABSTRACT FROM AUTHOR]

This article presents the findings of a study on oxide reduction utilizing a novel reducing plasma torch, employing greenhouse gases such as CO2 and CH4 as plasma gases. The primary aim of this investigation is to establish the viability of this approach. The innovative plasma torch was employed to reduce various oxides, including aluminum oxide, iron oxide, and titanium oxide, as well as a mixed oxide composition, employing a CO2/CH4 molar ratio of 1:1 within a spouted bed reactor. Following plasma treatment, X-ray diffraction (XRD) analysis was conducted to examine the metallic phases, notably titanium, iron, and aluminum. SEM–EDS observations were carried out to assess microstructural changes and identify elemental compositions pre- and post-plasma treatment. The results demonstrate that within the conical section of the reactor, titanium oxide experiences partial reduction, resulting in limited titanium production, while aluminum oxide and iron oxides (magnetite and hematite) undergo reduction to yield aluminum and iron, respectively. Thermodynamic calculations, performed using Factsage software version 8.3, were utilized to predict stable-phase formations following plasma treatment for each material. [ABSTRACT FROM AUTHOR]

The main objective of this study was to use flash boiling atomization as a new method to inject suspensions with high solid content into the high-power plasma flow. The water-based suspension was prepared with submicron titanium oxide particles with an average size of 500 nm. The investigated solid concentrations were 20, 40, 55 and 70 wt%. Two plasma torches operated at 33, 70 and 110 kW were used to investigate the effect of increasing power on the deposited microstructure and deposition efficiency. At low torch power, the deposition efficiency decreased with increasing solid concentration, and deposits with a high number of unmelted particles were obtained with 70 wt% suspensions. At high torch power, the deposition efficiency increased with increasing solid concentration, and dense deposits were obtained with 70 wt% suspensions. XRD analysis was performed on all deposits to determine the distribution of rutile and anatase phases. The percentage of the anatase phase varied from 35.7% to 66.9%, depending on the power input and solid concentration. [ABSTRACT FROM AUTHOR]

Current characteristics of a plasma-filled, high-current electron gun at different accelerating voltages and densities of plasma preliminary filling the space between the cathode and collector have been investigated. Multi-gap initiation of explosive emission is performed with the use of parallel operated, resistively decoupled arc plasma sources which electrodes and tube ceramic isolators are built-in to the explosive-emission cathode. Experiments have demonstrated operability of high-current electron gun with a new cathode assembly at accelerating voltage up to 30 kV and its good emissivity (average in area current density) which was approximately 1.4–2.4 times higher than an emissivity of traditional electron gun with plasma anode and multi-wire copper cathode. [ABSTRACT FROM AUTHOR]

The paper describes the design of a microscope for studying a betatron radiation source based on the PEARL femtosecond laser complex in the SXR and EUV wavelength range. The main optical element of the microscope is a spherical Schwarzschild objective a ×5 magnification. The device allows to study the size and spatial structure of the interaction area of laser radiation with matter, at a selected wavelength in the EUV or SXR range with a resolution of δx = 2.75 μm. The operation wavelength (λ = 13.5 nm) is set by multilayer X-ray mirrors. Thin-film absorption filters are used to suppress the background component of the signal. [ABSTRACT FROM AUTHOR]

Electric arc dynamics in plasma torches have an influence of the plasma jet stability and could impact coating properties. Depending on the plasma torch design, arc voltage fluctuations may vary from a hundred to only a few percent of the mean arc voltage. A cascaded-anode plasma torch particularly leads to very low arc voltage fluctuation, due to the presence of neutrodes limiting the amplitude of arc fluctuations. However, the electric arc dynamics and electrode erosion process are still poorly understood in this kind of plasma torches. The aim of this work is to refine the knowledge on the influence of the nozzle's diameter on electric arc dynamics and on zirconia-yttria coating properties. Two plasma-forming gas compositions were studied, connecting several analysis methods (end-on imaging, arc current and arc voltage time monitoring, plasma light fluctuations at nozzle exit, thermal balance evaluation and in-flight particles assessment) to coatings characterization (porosity and hardness measurements). Reducing the nozzle's diameter from 9 to 6.5 mm results in higher arc voltage fluctuations and lower thermal efficiency of the plasma torch. This is due to the warm plasma gas being more evenly distributed in the anode nozzle. After testing, surveys of the 6.5-mm-diameter nozzle show significant longitudinal wear, which may highlight an axial movement of the electric arc on the anode's surface, leading to high arc voltage fluctuations. Finally, the particle velocity is higher in a 6.5-mm-diameter nozzle, resulting in a lower particle temperature and a higher coating porosity. [ABSTRACT FROM AUTHOR]

Hybrid plasma spraying has been proved to provide novel coating microstructures as a result of the simultaneous injection of a dry coarse powder and a liquid feedstock into the plasma jet. Such microstructure contains both large splats originating from the conventional dry powder and finely dispersed miniature splats deposited from the liquid. This approach enables preparation of coatings from virtually all materials which are conventionally processed using plasma spraying. However, incorporation of materials susceptible to volatilization or decomposition at high temperatures is still challenging even using this concept due to the high thermal energy transferred toward the feedstocks to be deposited. Hereby, an innovative approach of incorporation of thermally sensitive materials into a coating sprayed using a high-enthalpy plasma torch is proposed using so-called external feeding deposition. As a case study, three coarse-powder-based feedstocks (Al2O3, YSZ, and Cr2O3) were complemented with three suspension-based feedstocks (MoS2, WS2, and ZnS, respectively) deposited using the novel method. In all three coatings, the additional thermally sensitive materials were successfully deposited, retaining their original structure and morphology, which was confirmed using scanning electron microscopy and X-ray diffraction. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental and theoretical investigations into the synthesis of silicon carbide using the energy of thermal plasma. The experimental investigations were conducted on a stand with 4 kW of power making it possible to have a thermal plasma flow with a bulk temperature of 5600 K. Regimes have been identified for the synthesis of silicon carbide and concentration of composite charge mixture components determining its yield. On the basis of processing experimental data, key characteristics have been calculated for the technological process of silicon carbide synthesis (time and load mass). [ABSTRACT FROM AUTHOR]

A new magnetic mirror machine named KAIMIR (KAIST mirror) has been designed and constructed at the Korea Advanced Institute of Science and Technology (KAIST) to study mirror plasma physics and simulate the boundary regions of magnetic fusion plasmas such as in a tokamak. The purpose of this paper is to introduce the characteristics and initial experimental results of KAIMIR. The cylindrical vacuum chamber has a length of 2.48 m and a diameter of 0.5 m and consists of three sub-chambers, namely the source, centre and expander chambers. A magnetic mirror configuration is achieved by electromagnetic coils with a maximum magnetic field strength of 0.4 T at the mirror nozzles and 0.1 T at the centre. The source plasma is generated by a plasma washer gun installed in the source chamber with a pulse forming network system. The typical discharge time is ~12 ms with a ~6 ms (1–7 ms) steady period. Initial results show that the on-axis electron density at the centre is 1019–20 m−3 and the electron temperature is 4–7 eV. Two parameters were varied in this initial phase, the source power and the mirror ratio, which is the ratio of highest to lowest magnetic field strength in the mirror-confined region. We observed that the increase of the electron density was mitigated for a source power above 0.2 MW. It was also found that the electron density increases almost linearly with the mirror ratio. Accordingly, the stored electron energy was also linearly proportional to the mirror ratio, similar to the scaling of the gas dynamic trap. [ABSTRACT FROM AUTHOR]

In this work, the long-term and repeated ablation properties of the YB 4 -Al 2 O 3 -Si 3 N 4 modified C f /HfC-SiC composites were characterized by air plasma torch at 2600 ℃ for 300 s, twice. Both the structural stability and the viscosity of the oxide layer affected the ablation resistance of the composites. The structural stability of oxide layer was improved by forming nano c -HfO 2 grains and the high-viscosity Al-Si-Y-O glassy phase, which increased the ablation resistance of the composites. However, the oxidation of Si 3 N 4 resulted in the formation of NO, NO 2 and excessive SiO 2 glassy phase, which both leaded to a porous structure and reduced the viscosity of the oxides layer. Hence, the ablation resistance of the composites was reduced with addition of the Si 3 N 4. [ABSTRACT FROM AUTHOR]

This paper refers to the topic of determining the kerf value and axis accuracy of a CNC plasma cutter for the cutting of 2, 4 and 6 mm thick plates of construction steel, aluminum and stainless steel. After the thorough description of the researched materials, a detailed experiment plan was created in the Design-Expert software package. After cutting the test samples the data were measured. Upon completion of the cutting, all test samples were measured, and the data regarding their dimensional deviations on x and y-axis and bore diameter deviations was tabularly shown and analysed with the Design – Expert software. Statistical analysis of the measured data was made so that the optimal kerf values and the equations which describe dimensional deviations for each material and thickness could be made, based on the dimensional deviation of the test samples. Along with the kerf values, analysis has also given insight in the accuracy of the x and y-axis of the machine. Finally, an algorithm for optimizing multiple criteria was utilized to determine the ideal kerf value for each material and thickness. The objective was to identify the precise kerf value that results in the highest possible accuracy for the dimensions of the workpiece in both the x and y directions, as well as for the bore diameter. [ABSTRACT FROM AUTHOR]

Titanium dioxide coatings (TiO2) were sprayed using a water-stabilized plasma gun (WSP) to form robust self-supporting bodies with the character of a ceramic disc capacitor (CDC). Agglomerated nanometric powder was used as feedstock. Argon was applied for powder feeding as well as coating–cooling to minimize the influence of ambient air. Stainless steel was used as a substrate, and the coatings were released after cooling. A more than three-millimeter-thick self-supporting TiO2 plate was observed using HR-TEM and SEM. Porosity was studied by image analysis on polished sections. Thermal post-treatment on the coating was conducted at a rather low temperature of 500 °C. The results of the subsequent dielectric measurement showed high permittivity, but this was strongly frequency-dependent and accompanied by a progressively decreasing loss tangent. On the other hand, the plasma-sprayed TiO2 exhibited persistent DC photoconductivity under and after illumination with a standard bulb. [ABSTRACT FROM AUTHOR]

Cold atmospheric pressure plasma (CAP) has attracted increased interest in recent years for possible biomedical, environmental and agricultural applications. A wide range of cold plasma treatment effects is observed in agricultural applications, like effects on the seed germination and seedling growth, but more systematic investigations are needed. The aim of this study was to identify the most appropriate combinations of the plasma source and duration of treatment positively affecting seed germination. In addition, the effect of cold plasma on the seedling growth and osmotic stress tolerance was studied. The seeds of three Bulgarian durum wheat cultivars were treated with cold plasma in twelve variants. The results obtained were processed statistically via two-way ANOVA. The treatment of seeds with a plasma torch for 20 s and the treatment with underwater diaphragm discharge for 5 min when the seeds were placed in both cameras in two different positions (relative to the electrodes between which the plasma is supplied, "+" and "−") have the greatest positive effect on the all traits related to germination. The analysis of variance reveals that the variation in germination energy, shoot length and root length after the cold plasma treatment of seeds is mainly due to the interaction between the genotype and treatment variant and to a small degree due to the genotype. The treatment of seeds with cold plasma improves the osmoregulation ability of cells and therefore increases the drought resistance of genotypes. [ABSTRACT FROM AUTHOR]

In the domain of re-entry and hypersonic vehicles, advancing material development requires comprehensive material testing to thoroughly understand the aero-thermo-chemistry at the surface. This paper overviews hypersonic, high-temperature activities conducted at the von Karman Institute for Fluid Dynamics (VKI) Plasmatron facility, employing three recently developed supersonic nozzles. These activities aim to augment VKI’s experimental and numerical capabilities in high-temperature material research, contributing to a deeper understanding of the chemical surface interactions, at stagnation and off-stagnation locations, during re-entry. The newly developed nozzles were 3D printed using an additive manufacturing (AM) aluminum alloy. The three nozzles serve distinct purposes: two conical ones of varying lengths are designed for stagnation point testing, while the third nozzle, adopting a semi-elliptical shape, is tailored for off-stagnation point testing. The initial section of the paper focuses on designing, manufacturing, and simulating these nozzles, then we characterize the nozzle flow and compare with simulations, while the subsequent part will delve into showcases of recent activities conducted in the Plasmatron facility utilizing these distinct nozzle configurations. [ABSTRACT FROM AUTHOR]

The magnetic system of an open trap usually includes expansion sections located between high-field magnetic mirrors and end surfaces that receive plasma. In the GOL-NB device, an arc plasma gun is located in one of the expanders, which creates a low-temperature starting plasma in the confinement area. The parameters of the surface plasma sheath affect the electrical connection of the confinement area with the walls and, thereby, affect the contribution of the line-tying effect to the plasma stability and the longitudinal energy losses from the trap. The experiments with additional hydrogen injection into the plasma gun were carried out at GOL-NB. We observed a radiating plasma formation detached from the surface, which visually corresponds to that in radiating divertors in tokamaks. In both standard and detached modes, decaying plasma existed near the receiving electrodes during the entire observation time after the discharge current was terminated. In the central trap of GOL-NB, some structures in the Fourier spectrogram of magnetic fluctuations manifest earlier in the detachment mode than in the standard mode and have lower frequencies. We associate these structures with the onset of interchange-like modes due to the loss of plasma stabilization by the line-tying to the conducting ends. The observed plasma response to the additional gas supply confirmed our understanding of the line-tying effect as the main factor stabilizing the plasma core in the initial phase of density accumulation in the central trap. [ABSTRACT FROM AUTHOR]

The astonishing safety and capacity characteristics of solid-state-batteries are encouraging researchers and companies to work on the manufacturing, development, and characterization of battery materials. In the present work, the effects of laser beam interaction with a liquid feedstock plasma-sprayed ceramic solid-state-battery (SSB) material coating were studied. Lithium Titanium Oxide (LTO) in the form of an aqueous suspension consisting of submicron powder particles was plasma-sprayed for the first time using a high-power axial III plasma torch on an aluminum substrate. The plasma-sprayed LTO coating suspension was subsequently post-processed using a fiber laser. The energy input of the laser beam on the surface of the deposited layer was the main variable. By varying the laser power and laser processing speed, the energy input values were varied, with values of 3.8 J/mm2, 9.6 J/mm2, 765.9 J/mm2, and 1914.6 J/mm2, and their effects on some key characteristics such as laser-processed zone dimensions and chemical composition were investigated. The results indicated that changing the laser beam parameter values has appreciable effects on the geometry, surface morphology, and elemental distribution of laser-processed zones; for instance, the highest energy inputs were 33% and 152%, respectively, higher than the lowest energy input. [ABSTRACT FROM AUTHOR]

Turquoise hydrogen is produced through a process of separating carbon into solid carbon based on fossil fuels and refers to hydrogen that does not produce carbon dioxide. In this study, the characteristics of turquoise hydrogen production through a methane thermal cracking reaction using an arc plasma torch were investigated. The plasma torch operated stably under high voltage and transport gas flow conditions. The composition of the gas generated from the methane plasma reaction was analyzed using an online IR gas analyzer and GC-FID. The experimental results show that the hydrogen yield decreased to 16.4% as the methane feed rate increased but increased to 58.8% as the plasma power increased. Under these conditions, the yield of solid carbon, a valuable byproduct, was also shown to increase to 62.9%. In addition, solid carbon showed high-temperature heat-treated characteristics based on its generation location. Carbon oxides such as CO and CO2 are rarely generated under any experimental conditions. Consequently, it can be considered that plasma thermal cracking is a promising technology for CO2-free hydrogen production and a valuable solid carbon. [ABSTRACT FROM AUTHOR]

In this study, the plasma torch is utilized for the preparation of highly pure ZrO 2 from zircon (ZrSiO 4). The incorporation of H 2 into the discharge gas Ar improves the plasma physical parameters and serves as a reducing agent to promote the irreversibility of the pyrolysis reaction of ZrSiO 4. ZrSiO 4 powder is fed internally into a DC arc plasma torch through a powder feeder device. The DC torch generates thermal plasma that can fully heat all the ZrSiO 4 within a short period for pyrolysis, extraction, and separation, eventually producing high-purity ZrO 2. According to the results, the addition of H 2 to the working gas increases the material temperature in the flame by increasing the plasma temperature, thereby promoting the pyrolysis of ZrSiO 4. The temperature of the material is 2500–2600 °C, which is higher than the boiling point of the pyrolysis product SiO 2 while maintaining the high melting points of ZrSiO 4 and ZrO 2. Furthermore, H 2 plasma acts as a reducing agent in the pyrolysis reaction, where it combines with the O of the product to prevent the reversibility of the pyrolysis reaction of ZrSiO 4 and retains only ZrO 2. [ABSTRACT FROM AUTHOR]

Plasma technologies have drawn attention as a possible way for biomass/waste conversion into valuable intermediate products, which could partially satisfy the growing energy demands. Thus, this experimental research aimed to determine the ability to gasify wood pellets to synthesis gas in the thermal air plasma environment. The influence of the plasma torch power, plasma-forming gas flow rate, and the equivalence ratio on biomass gasification was analyzed. The synthesis gas generation varied between 59.95 and 62.51%, while the H2/CO ratio ranged from 0.68 to 0.8. The producer gas's highest H2 and CO concentrations were 26.6 and 33.35%, respectively, giving the H2/CO ratio of 0.8. The lower heating value of the produced synthesis gas ranged from 7.62 to 8.82 MJ/Nm3. The carbon conversion efficiency and the energy conversion efficiency were equal to 85.3–97.2% and 29.23–30.57%, respectively. The specific energy requirements varied between 165.47 and 195.61 kJ/mol of synthesis gas. Moreover, the energy and mass balance evaluation showed that generated producer gas could produce 15–18 kWh and 111–114 kWh of electrical and thermal energy, respectively, when 20.73 kg/h of wood pellets is gasified. Also, 28 and 33% of the electricity required for the air plasma formation can be received using producer gas in an internal combustion engine and microturbine. [ABSTRACT FROM AUTHOR]

Foliar fertilizing is very important to supply apple plants with calcium and micronutrients. The most cost-effective approach to this is the application of the fertilizers in tank mixtures with plant protection chemicals. Plasma-activated water (PAW) has great potential for the use in the agriculture. We used two type of PAWs, PAW1 (made using underwater electrical discharge in an aqueous KNO3 solution and includes reactive nitrogen species and platinum nanoparticles) and PAW2 (made using a plasma torch with nitrogen gas makeup and contains reactive nitrogen species but not metals). We studied the impact of two PAW types on the contents of Ca, B, Mn, Fe, and Co in leaves and Ca, Mn, Fe, Zn, and Mo in fruits sprayed with tank mixtures containing the fertilizers. We also tested the efficiency of PAW in the control of apple scab when applied as tank mixtures with plant protection chemicals. The application of the PAWs significantly increased foliar Ca when the PAW was mixed with Ca-containing formulations (spraying PAW1 containing Ca increased leaf Ca by up to 21%, and PAW2 up by to 9% compared to Ca spraying without PAW). The largest fruit Ca increase was in the variant treated with PAW1 with a micronutrient spraying program (up to 143%). The PAW treatments enhanced the baseline mineral contents of the plants even when they were not sprayed with the nutrients. PAW1 mainly increased the nutrient contents of the apple fruits. PAWs have proven to be efficient for the control of apple scab, thereby reducing the demand for fungicides. The scab damage to the leaves and fruits was similar in plants treated with PAWs without fungicides (1.7–1.9% on the leaves and 1.6–1.8% on the fruits) compared to the conventional chemical scab control (0.9% leaves and 0.6% fruits) and was significantly lower than in the untreated control (9.3% on leaves and 11.9 on fruits). [ABSTRACT FROM AUTHOR]

Plasma-assisted aerosol deposition (PAD) is a new ceramic coating technology that utilizes a low-pressure induction plasma jet to accelerate particles toward the substrate and form a coating. This plasma jet was generated by a radio frequency (RF) inductively coupled plasma torch under reduced pressure. Although the particle velocity was expected to directly influence the phenomena of particle collision, adhesion, and coating formation, it has not been investigated systematically. Thus, we aimed to clarify the velocity of particles accelerated by a subsonic or supersonic low-pressure induction plasma jet using a convergent-divergent (C-D) nozzle. The particles' velocity colliding with the substrate was measured using a time-of-flight method. The effects of the C-D nozzle, input RF power, and carrier gas flow rate on the particle velocity were investigated for alumina and yttria-stabilized zirconia particles. The use of the C-D nozzle increased the particle velocity, significantly, while the input RF power was an insensitive parameter for the particle velocity. This study implies the introduction of the C-D nozzle is effective on the particle acceleration in PAD. [ABSTRACT FROM AUTHOR]

The double-chamber arc plasma torch (DCAPT) is a promising arc source due to its high energy efficiency and low erosion rate. It has been widely used in various fields including coal powder ignition, boiler heavy oil-free ignition, and production of sheet-shaped carbon materials, among others, but research on its micro-discharge characteristics is still insufficient. In this work, a magnetically-stabilized DCAPT with a quartz window on the inner electrode is designed and studied, in order to investigate the effects of magnetic field position and intensity, discharge current, gas flow rate, electrode diameter, and electrode polarity on its discharge characteristics. Results show that both the volt-ampere characteristics and thermal efficiency of DCAPT exhibit a strictly decreasing trend, and both of them can be accurately predicted using similar theoretical approaches. The discharge characteristics of DCAPT differ significantly for different polarities. When in reverse polarity, the outer cathode arc root attaches to the outlet, resulting in an increased arc length and greater randomness in the arc-root fluctuations. As a result, the arc length, voltage, thermal efficiency, and voltage fluctuations are all greater than with normal polarity. Within the experimental range of the parameters, the thermal efficiency of DCAPT is between 40 and 74%. Due to the cathode's "easily mobility" characteristic, the rotation speed of the cathode arc root is always greater than that of the anode, resulting in higher thermal losses for the cathode than for the anode. This is the primary source of thermal loss and the main factor contributing to the rapid erosion of the cathode in the DCAPT. This study reveals the correlation between the volt-ampere characteristics, thermal characteristics, and dynamic evolution of the DCAPT. The research findings have significance for guiding the structural design, parameter selection, and choice of application of this type of plasma torch. [ABSTRACT FROM AUTHOR]

While numerous studies are available on methane pyrolysis chemical kinetics and the effect of plasma parameters on graphene synthesis, a comprehensive understanding of the formation mechanism remains elusive without in situ analysis. This study aims to utilize a sampling probe for the first time to collect graphene locally on transmission electron microscopy grids and perform a localized sampling and analysis of the gas composition (during graphene synthesis) using mass spectrometry. This technique provides a 3D tracking of methane pyrolysis in radiofrequency inductively coupled thermal plasma reactor for graphene production. Response surface methodology based on central composite design is employed to obtain a 3D visualization of the synthesis process. Quadratic and cubic models are developed, followed by comprehensive analysis of variance. A comparison of the gas-phase chemistry resulting from the in situ measurements with thermodynamic equilibrium calculations reveals that the process is controlled by thermochemical kinetics. H2, C2H2, C2H4, C3H6, and C6H6, as well as residual CH4, are the main hydrocarbons found in the graphene nucleation zone. The primary pathway for methane pyrolysis and graphene formation in RF plasma is through H2 and C2 hydrocarbons, while graphene nucleation and growth reactions are terminated 350 mm from the plasma torch nozzle exit. Morphology, quality, mean particle size, and the number of layers of the produced graphene samples, locally collected at different locations by 3D axisymmetric probe scanning, were investigated using TEM, high-resolution TEM imaging, and Raman analysis. The gathered information is highly valuable for plasma reactor design. [ABSTRACT FROM AUTHOR]

Laminar plasma torch has been widely employed to generate laminar plasma jet with notable advantages, e.g. high specific enthalpy, long jet length, low axial temperature gradient, etc. However, it is challenge to maintain the stability of laminar plasma jet due to the existence of different modes of arc fluctuation, e.g. steady mode, take-over mode and restrike mode. Previous studies on arc fluctuation mainly regard the arc current as a constant value, ignoring the influence of the dynamic control performance of the DC power supply on the variation of the actual arc current. The authors found that when the variation of the arc current exceeds the control capability of the power supply, the arc column expands and contracts periodically, exhibiting a new mode of arc fluctuation named arc column oscillation (ACO) in this paper. To reveal the characteristic phenomena, conditions of the laminar plasma torch and reason for the occurrence of ACO, experiments were conducted on a home-made DC laminar arc plasma torch. Results showed that ACO occurs when the operating conditions were low current, high gas flow rate, and high nitrogen proportion of the plasma-forming gas. It was found that ACO shows characteristics of high fluctuation of the arc current and the pressure in the cathode cavity, and periodic expansion and contraction of the arc column as observed by the high speed camera. Additionally, the arc current and pressure in the cathode cavity oscillated at the same frequency along with the occurrence of ACO, showing the coupling between the arc current and the pressure in the cathode cavity. Furthermore, with the decrease of the arc current, increase in the gas flow rate, and increase in the nitrogen proportion of the plasma-forming gas, the fluctuation of the arc current tends to increase when the ACO occurs. [ABSTRACT FROM AUTHOR]

We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and specific impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in the very low Earth orbit. A dual mode operation is achieved by leveraging propellant gasdynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely, magneto-deflagration and magneto-detonation, respectively. These modes form the basis of using gasdynamics to enable responsive thruster performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes as gas is allowed to expand in the thruster, with exhaust velocities ranging from 10 to 55 km/s in the deflagration and detonation regimes, respectively. Simulations of the processed mass bit offer the first glimpse into possible thruster performance and trade-offs between specific impulse and thrust. An impulse bit tunability of ∼ 22 % is predicted, with differing propellant fill fractions when operating in a burst mode. [ABSTRACT FROM AUTHOR]

Experiments on heat transfer in supersonic underexpanded jets of high-enthalpy nitrogen with ceramic samples based on HfB2–SiC are carried out at the induction RF plasmatron VGU-4 (Ishlinsky Institute for Problems in Mechanics of the Russian Academy of Sciences) at a pressure in the pressure chamber of 8.5 hPa, a gas flow rate through the discharge channel of 3.6 g/s, and an RF power of the plasma torch generator for anode supply of 64 kW. Three heat transfer modes are implemented using water-cooled conical nozzles with outlet diameters of 30, 40, and 50 mm. For the experimental conditions in supersonic modes, using a numerical method within the framework of the Navier–Stokes equations and simplified Maxwell equations, we simulate nitrogen plasma flows in a plasmatron discharge channel and the flow of dissociated nitrogen underexpanded jets around a cylindrical holder with a ceramic sample. From a comparison of the experimental and calculated data on heat fluxes to the surface of three samples, the effective coefficient of heterogeneous recombination of nitrogen atoms on the surface of ultra-high-temperature ceramics (UHTCs) at temperatures of 2273–2843 K is determined. [ABSTRACT FROM AUTHOR]