Arc Discharge Plasma Research Articles

Investigation of the characteristics of an indirect plasma torch

The main task of creating plasma technologies is to improve the operation parameters of its main element - the plasma torch, which is achieved by designing and constructing its main nodes. The paper analyzes the principles of designing a plasma torch and investigates the characteristics of an arc discharge plasma torch. The possibilities of increasing the thermal stability of the anode structure are considered; the speed and trajectory of powder particles are studied; the axial introduction of the powder through the cathode and the thermal stability of the cathode are studied. Using the finite element method, the effect of the anode shape on the service life of the plasma torch is studied by estimating the heat release power under the condition above the melting temperature of copper (anode). The optimal anode geometry for effective cooling of the unit with radial inlet and outlet of the coolant is determined. The influence of the thermal load on the cathode part of the plasma torch is studied, the thermophysical characteristics of the cathode on the operational characteristics of the plasma torch during the thermal load are taken. The dynamics of the particle by axial injection of the powder through the cathode is calculated, and the dynamics of the heating of the powder particle is determined. The output of the carrier gas is stabilized by a swirler and has great dynamics and is located in the high-temperature part of the arc. The trajectory of the movement of a powder particle in the nozzle area is calculated, which corresponds to the average value of the velocity ≈450-500 m/s. It is found that an increase in the cathode diameter from 3 to 5 mm reduces the thermal load by 50%.

Effect of Prebreakdown Time on Shock Wave Generation Characteristics of Underwater Plasma Sound Source

Acoustic array bunching is an effective method to realize the directional radiation of underwater plasma sound source (UPSS). The prebreakdown time is one of the decisive factors for the performance of acoustic array bunching. The working characteristics of the underwater plasma sound source and the prebreakdown process of underwater plasma arc discharge are deeply analyzed. The precondition of plasma sound source array bunching is given by analyzing the waveforms of electrical signals and acoustic signals. Through the experiments of arc discharge based on different aqueous solutions, a feasible scheme of underwater plasma sound source array bunching in salt water is proposed. Through the arc discharge experiments based on different system discharge parameters, the variation of prebreakdown time under the influence of different charging voltage, conductivity, and other parameters was studied. The experimental results show that the prebreakdown time decreases with the increase of charging voltage and conductivity. At the same time, the discharge current increases, the oscillation time decreases, and the energy injection rate on the electrode accelerates. The research results are helpful to understand the prebreakdown mechanism of plasma sound source and optimize the underwater plasma sound source array bunching scheme and the acoustic shock wave waveform.

Gliding Arc Plasma Discharge Conditions on Microbial, Physicochemical, and Sensory Properties of Shrimp (Litopenaeus vannamei): In Vivo and In Vitro Studies

Gliding Arc Plasma Discharge Conditions on Microbial, Physicochemical, and Sensory Properties of Shrimp (Litopenaeus vannamei): In Vivo and In Vitro Studies

Study on the mechanism of shock wave and boundary layer interaction control using high-frequency pulsed arc discharge plasma

This paper studies the response characteristics of shock wave and boundary layer interaction (SWBLI) controlled by high-frequency pulsed arc discharge (PAD) in a Mach 2.5 flow. The dynamic evolution of SWBLI disturbed by arc plasma energy deposition was captured, and the controlling mechanism under different exciting power and frequency was explored. The results showed that the blast wave induced by PADs had a strong impact on SWBLI structures and distorted the separation shock wave. During the downstream propagation, the controlling gas bubbles (CGBs) delivered a continuous thermal excitation to the boundary layer and reached the maximum penetration depth near the semi-cylinder. The arc discharge in the SWBLI region induced larger energy deposition, which made the heating zone obtain the highest initial temperature and longest heating duration. Under the plasma condition of 1 × 1011 W/m3/15 kHz, both the upstream part of the shear layer and the foot portion of the reattachment shock wave were removed. When setting the excitation to 2.5 × 1010 W/m3/60 kHz, a thermal exciting surface of merged CGBs was formed and the separation shock wave was completely replaced by an equivalent compression-wave system. A better drag-reduction effect on the flow field would be produced by the actuator with an increased operating power or frequency, and a drag reduction rate of nearly 25.5% was achieved under the 2.5 × 1010 W/m3/60 kHz control condition.

Catalyst-free production of ammonia by means of interaction between a gliding arc plasma and water surface

This work reports a study on using a gliding arc plasma reactor to produce ammonia from nitrogen plasma and a water medium without using a catalyst. During the gliding arc plasma discharge, a plasma plume was formed, and vibrational and rotational excitation was observed at the tip of the plasma plume that touched the water below. This arrangement helped the formation of ammonia. The ammonia concentration was 2.12–5.69 ppm, and its production rate varied in the range of 0.63–0.68 mg h−1, having energy efficiency in the range of 0.0249–0.0268 g-NH3 kWh−1, depending on the plasma exposure time. The vibrational temperature increased from 2632 K (near the gas entry zone) to 3778 K (at the tip of the plasma plume interacting with the water), corroborated by the enhanced distribution of electron energy for vibration excitation (≈24%), compared to that for electronic excitation (≈0.03%). The electron temperature dropped from 1.38 eV to 0.76 eV at the plasma zone interacting with the water. This work demonstrates the application of gliding arc plasmas to generate eco-friendly ammonia (green ammonia), and the reactor proves to be promising for further optimization in the future.

An innovative procedure for synthesizing Al70M20(Fe, Co)Cr10 amorphous nanoparticles by arc discharge method and investigation of their magnetic, hardness, and corrosion resistance properties

Al70Fe20Cr10 and Al70Co20Cr10 amorphous nanoparticles were prepared by plasma arc discharge process under arc current of 50 A and 1 atm. pressure in liquid nitrogen medium. XRD patterns of the as-prepared powders exhibit amorphous nature. According to TEM images, the Al70Fe20Cr10 and Al70Co20Cr10 amorphous nanoparticles have a spherical shape with a mean size of 27 and 35 nm, respectively. Static magnetic measurements using a vibrating sample magnetometer (VSM) indicate that the Al70Co20Cr10 amorphous alloy has a higher saturation magnetization of 9.3 emu/g and a lower coercive field of 14 Oe compared with 3.8 emu/g and 45 Oe for the Al70Fe20Cr10 amorphous alloy. In contrast, the Al70Fe20Cr10 amorphous alloy has a higher hardness and shows approximately 20 times more corrosion resistance than the Al70Co20Cr10 amorphous alloy.

Features of Interaction of Molecular Oxygen with Condensation Surface in Low-Pressure Arc Discharge Plasma

Features of Interaction of Molecular Oxygen with Condensation Surface in Low-Pressure Arc Discharge Plasma

Influence of N-doping on dielectric properties of carbon-coated copper nanocomposites in the microwave and terahertz ranges

Carbon-coated Cu nanocomposites (Cu@C NCs) consisting of core-shell nanoparticles and nanorods were synthesized by arc discharge plasma under an atmosphere of He and H2 gas, and the N-doping of them was achieved by a post-treatment process using ureal as the precursor. The concentration of N in the N-doped samples varies in the range of 0.62%–2.31 % (in mole), with a transformation from pyrrolic N to graphitic N when increasing the relative content of ureal. Dielectric properties of the NCs without or with N-doping in the microwave and THz bands were investigated. The N-doped samples achieve the enhanced dielectric loss in both microwave and THz bands. In the microwave band, dielectric loss was dominated by interfacial polarization, dipolar polarization, and conduction loss, while in the THz band, plasma resonance, ionic polarization and conduction loss are responsible for the dielectric loss, with a strong absorption characteristic dominated by conductive effect.

(Digital Presentation) Water Treatment through the Arc and Pulsed Spark Discharge

Water deterioration and depletion are accompanied by population growth and fast urbanization, posing major environmental problems. The prevalence of water-borne infections remains high, making it critical to discover effective ways of disinfecting water thoroughly. The main methods for inactivating a wide spectrum of harmful bacteria are chemical, physical, electrochemical, and radical. Conventional decontamination methods not only fail to completely disinfect water but also have several drawbacks, including the generation of disinfection byproducts; the complexity of disinfection reactor design; high energy consumption; and high running expenses. As a result, a versatile approach should be developed to overcome the limitations of current decontamination methods while also being efficient against a variety of diseases. Plasma-based water treatment has recently emerged as a possible alternative to traditional approaches. Plasma has proven to be more effective than conventional oxidants and disinfectants, both directly and indirectly. Plasma-related effects vary depending on the type of discharge, device settings, and process parameters. Electrical discharges are one of the most effective water treatment treatments. To this end, two plasma discharges, i.e., arc and pulsed spark discharge, are used for the treatment of synthetic contaminated water with microorganisms, which can be used for naturally contaminated surface water. Our results revealed that in comparison to arc discharge, pulse spark discharge produces more extreme acidic conditions by lowering the pH of water samples as well as a more reactive environment, which results in greater antibacterial efficacy. Furthermore, water samples treated with arc discharge had greater temperatures than water samples treated with pulse spark discharge, indicating that temperature was not a critical effector in the plasma-based sterilizing process.

Characteristics of liquid‐phase continuous arc discharge plasma

AbstractLiquid‐phase discharge has the advantages of high plasma density, simultaneous generation of multiple physical and chemical effects, and high gas‐liquid mass transfer efficiency. However, the large‐capacity treatment of liquid by plasma has always been a research difficulty. In this study, liquid‐phase continuous arc (LCA) discharge plasma is realized for the first time, which can quickly propagate for a long distance in liquid. To better understand this new type of liquid‐phase discharge, the time‐space characteristics, electrical characteristics, optical characteristics and particle characteristics of the LCA discharge plasma are diagnosed. The results show that the LCA discharge plasma can achieve a rapid propagation over 1 m in the liquid, and the propagation time is on the order of milliseconds. Meanwhile, the discharge can directly generate a variety of active species (·OH, ·O, ·H, H2O2) in the liquid, which can be continuously produced as the plasma moves. The LCA discharge plasma has good application prospects in water treatment, energy conversion, and so on.

Properties of rapid arc discharge plasma nitriding of AISI 420 martensitic stainless: effect of nitriding temperatures

Martensitic stainless steels (MSS) with excellent mechanical properties are potential candidates used in the nuclear, marine, aeronautical, and aerospace industries. However, surface treatments are needed to improve the wear performance of MSS. Arc discharge plasma nitriding (ADPN) was applied on selected AISI 420 stainless steel to improve the wear performance without reducing its original corrosion resistance. To avoid the formation of the CrN phase, the ADPN was performed at temperatures ranging from 400 °C to 460 °C for 1 h. The effects of nitriding temperature on the structural, mechanical, and tribological properties of the nitrided layers were examined by X-ray diffraction (XRD), Scanning electron microscope (SEM), Vickers microhardness tester, and ball-on-disk tribometer, respectively. Potentiodynamic polarization in a 3.5% NaCl solution was used to assess corrosion resistance. The surface of the specimen nitrided at 400 °C is ε-Fe2-3N phase while that of specimen nitrided at higher temperature is αN phase. The thickness of the nitrided layer could reach 15 μm in 1 h at 460 °C in virtue of the high-density and high-energy nitrogen plasma, which showed an extremely high nitriding efficiency. The brittle Fe2–3N phase layer on specimen nitrided at 400 °C contributes to unsatisfactory wear resistance with severe abrasive wear behavior, however, excellent corrosion properties. The specimen nitrided at 460 °C shows superior wear resistance but degraded corrosion property due to Ti particles covered microstructure. The specimen nitrided at 420 and 440 °C possess desirable wear and corrosion performance, as well as excellent surface quality.

Spectroscopic Diagnosis of Arc Carbon and Magnesium Plasma

This research aims to investigate parameters for magnesium (Mg) carbon (C), and carbon/magnesium plasma produced by the exploding electrical wire (EEW) technique. In this work, C and Mg nanoparticles were synthesized. The plasma spectra with three different current values (50, 75 and 100A) were recorded using optical emission spectroscopy (OES). The plasma electron temperature (Te), electron density (ne), plasma frequency (fp), Debye length (ℷD), and Debye number (ND) provided by arc discharge plasma were calculated. Boltzmann plots were used to calculate the electron temperature (Te); electron density (ne) was calculated by Stark broadening . The results showed that the electron temperature and electron density increased with the increase of current. For carbon plasma, Te increased from (1.243 to 1.533) eV, and ne increased from (8.762 to 9.857) cm-3. Te for magnesium plasma increased from (0.508 to 0.724)eV and ne increased from(6.700 to 10.420) cm-3. When the magnesium strip was exploded in carbon suspension, Te increased from (0.744 to 0.851) eV, and electron density was raised from (5.738 to 9.304)cm-3.

Plasma assists titanium nitride and surface modified titanium nitride nanoparticles from titanium scraps for magnetic properties and supercapacitor applications

Plasma methods are efficient processing for metal recovery from metal scrap, bearing minerals, electronic waste, etc. In this work, pure titanium nitride nanoparticles (TiN NPs) were synthesized from titanium scraps by the thermal plasma arc discharge (TPAD) method. TPAD synthesized TiN NPs have a highly crystalline nature with cubic and spherical morphologies with average particle sizes of 30–100 nm. Further, prepared TiN NPs involving surface modification (SM) or etching processes were investigated by using the non-thermal DC glow discharge plasma technique with air atmosphere at different processing times. SM@TiN NPs have a comparatively low crystalline, which was confirmed from the powder X-ray diffraction technique. SM@TiN NPs have very interesting core shell morphologies, which are due to the surface interactions of ionized air molecules. TiN and SM@TiN NPs have room-temperature ferromagnetic properties with high saturation magnetization (Ms) up to 2.6 and 3.0 emu/g and very high coercivity (Hc) of 235.5 Oe, respectively. TiN and SM@TiN NPs have superior energy storage performance with an outstanding specific capacitance of 192.8 and 435.1 F/g at a current density of 2 A/g with pseudocapacitive behavior. These results reveal that TiN and SM@TiN NPs have highly promising electrodes for supercapacitor applications.

Regulation of structural and terahertz properties of TiC nanoparticles by carbon-coating and nitrogen-doping

Carbon-coated titanium carbide nanocomposites (TiC@C NCs) were synthesized by arc discharge plasma under an atmosphere of Ar and CH4 gas, and nitrogen-doped carbon-coated titanium carbonitride nanocomposites (Ti(C,N)@NC NCs) were also obtained using a mixture gas of N2 and CH4. Terahertz (THz) optical and dielectric properties of these nanostructures were investigated using a THz time-domain spectrum system, and the extracted conductivity was analyzed to understand the transport mechanism. The dielectric response in these nanostructures is dominated by ionic polarization with a relaxation behavior, and absorption characteristic is free carrier absorption dependent on conductivity. Ti(C,N)@NC NCs achieve the enhanced dielectric response and high absorption loss due to nitrogen-doping increasing charge disorder and conductivity. AC conductivities of the samples were fitted to the universal power low function and indicated that the transport mechanism is electronic hopping.

Simulation of Thermal Field in Eutectic Microwave Bonding for Electrical Connection of Photovoltaic Cells

Sustainable development requires green energy and low carbon footprint in manufacturing sector of photovoltaic systems. The electrical connections of photovoltaic cells need to have low electrical resistance in order to reduce the electrical losses and therefore to improve the performance of the photovoltaic panels. This paper aims to present researches related to bonding of wires that connect solar cells by using microwave technology. The microwave bonding has the main advantage that offers fast bonding but, in the same time, this technology does not offer stability of the thermal heating. Two different unwanted phenomena like thermal runaway and plasma arc discharge often lead to the damaging of copper and aluminum wires used in electrical connection. The study presented in this paper is focused on simulation of the thermal field developed in copper wires in order to optimize the bonding process and increase the quality of products. The simulation of the thermal field has been done using Fourier equations for conducting heating in copper materials and eutectic alloys. The simulation model has been validated through experimental heating using a 6 kW water-cooled microwave generator controlled by a matching load auto-tuner for best transfer of the power from generator to copper wires. The temperature has been measured in real time using an infrared pyrometer for metals with 2.3 μm spectral range and measurement range between 0o C and 7000 C. The study is finalized with elaboration of mathematical model for microwave-injected power as function for temperature developed in copper wires that can be applied with success in further microwave bonding applications of copper wires. In addition, the electrical resistance of bonded wires was measured in order to collect feedback for improving the microwave bonding process.

Experimental and Numerical Study on Incident Shock Wave/Boundary Layer Interaction Control

This study was designed to explore the control effect of pulsed arc discharge plasma actuation on the incident shock wave/boundary layer interaction (ISWBLI). Research was conducted on an ISWBLI flow field with 10 kHz single-channel pulsed arc discharge plasma actuation and pulsed arc discharge plasma actuation array applied at Mach 2.0 experimentally and numerically. In the investigation, high-speed schlieren flow field visualization technology was adopted, focusing on the change in shock wave intensity caused by plasma actuation. Combined with the detached eddy simulation (DES) method, the numerical simulation focused on the regulating effect of plasma actuation on the separation zone. The key research results showed that, in terms of the spatial flow field, the simulation results were consistent with the experimental results. The single-channel actuation could only just achieve the control effect on the ISWBLI, while array actuation effectively weakened the shock wave intensity. Furthermore, the ISWBLI separation zone in the base flow field was crescent shaped. Its length at the middle of the flat plate was longer than that at the two sides. It was identified that, after applying single-channel actuation, the start of separation slightly moved forward. Similarly, after the application of array actuation, the start point of separation at the middle section in a spanwise direction moved forward by about 19 mm. The length of the separation zone increased by 30 mm but reduced at the two sides. Its influence, spanwise, was also significantly diminished.

Synthesis of Submicron Boron Carbide by the Non-Vacuum Method with Indirect Supply of the Thermal Energy of a DC Arc Discharge

The results of experimental studies demonstrating the possibility of obtaining boron-carbide powder by treating a mixture of carbon and amorphous boron containing a small amount of boron oxide with DC arc discharge plasma are presented. A feature of the applied nonvacuum electric-arc method for the synthesis of boron carbide is its implementation in an open air environment due to achievement of the effect of screening the reaction zone with gaseous oxide and carbon dioxide. In this case, the initial reagents are heated to the required temperatures by a DC arc discharge plasma burning in the immediate vicinity of the initial-material mixture in the cavity of the graphite crucible. The resulting material contains particles of boron carbide with a size in the submicron range, which are characterized by the “shell–core” type structure. The scheme of the discharge circuit of a laboratory reactor with horizontal arrangement of electrodes and an indirect supply of thermal energy to the initial reagents described in the paper makes it possible to significantly increase the content of the boron-carbide phase and reduce the content of the graphite impurity phase.

Thermally stable carbon-coated SiC/polydimethylsiloxane nanocomposites for EMI shielding in the terahertz range

Rapid development of terahertz (THz) technologies makes electromagnetic interference (EMI) shielding increasingly critical for control of electromagnetic (EM) radiation and reduction of EM pollution. In this study, carbon-coated silicon carbide nanoparticles (SiC@C NPs) are synthesized by arc-discharge plasma and dispersed into a polydimethylsiloxane (PDMS) matrix to fabricate SiC@C/PDMS nanocomposites (SiC@C/PDMS NCs). The NCs demonstrate excellent THz shielding/absorption performances in virtue of the SiC@C NP fillers and composite structure in a wide range from 0.5 to 3.0 THz. The maximum shielding efficiency and reflection loss in the range from 0.5 to 3.0 THz reach up to 44.5 and 19.0 dB on average, respectively, for the NC with a loading of 10 wt.% SiC@C NPs and 0.6 mm thickness. The SiC@C/PDMS NCs possess a high thermal stability in air, as well as lightweight and hydrophobicity. This work would provide an insight into the functionalization of the SiC@C NPs as high-performance THz shielding materials.

Features of a burning electric arc superimposed on gas discharge with liquid electrolyte cathode

The conditions for burning an electric arc in a discharge plasma with a solution cathode have been studied. Both discharges were connected to the same metal anode. The electric arc burned in the current range of 5–10 A. The discharge current with a solution cathode varied within 8-15 A. In the experiments, aqueous solutions of common salt were used. The specific electrical conductivity of the solutions was 10–15 mS/cm. Spectral investigations of arc plasma radiation and discharge with a solution cathode have been carried out. Calculations of the parameters of the electron gas in the plasma column have been performed.

Efficient Synthesis of WB5-x-WB2 Powders with Selectivity for WB5-x Content.

We proposed an efficient method toward the synthesis of higher tungsten boride WB5-x in the vacuumless direct current atmospheric arc discharge plasma. The crystal structure of the synthesized samples of boron-rich tungsten boride was determined using computational techniques, showing a two-phase system. The ab initio calculations of the energies of various structures with similar X-ray diffraction (XRD) patterns allowed us to determine the composition of the formed higher tungsten boride. We determined the optimal parameters of synthesis to obtain samples with 61.5% WB5-x by volume. The transmission electron microscopy measurements showed that 90% of the particles have sizes of up to 100 nm, whereas the rest of them may have sizes from 125 to 225 nm. Our study shows the possibility of using the proposed vacuumless method as an efficient and inexpensive way to synthesize superhard WB5-x without employing resource-consuming vacuum techniques.