Arc Plasma Research Articles

Effect of Cold Plasma on the Germination and Seedling Growth of Durum Wheat Genotypes

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.

Structural design and adaptive tracking control of automatic welding robot for liquefied natural gas containment system

Liquefied natural gas (LNG) is commonly transported by LNG carriers and stored in cargo containment systems. The primary barrier of the MARK III cargo containment system is welded to a closed space with corrugated stainless steel plates. To meet the requirements of excellent sealing and thermal insulation for cargo containment, the welding process of the corrugated plate need to be strictly controlled, which poses a challenge to the development of related welding equipment. In this paper, we present a new five-axis automatic welding robot system used for plasma arc welding on corrugated surfaces. The moment transfer scheme of the dual linkage mechanism makes the rotary movement of the robot more accurate and stable which gives the system with simpler control algorithm and better overall force characteristics. To ensure tracking accuracy, a novel sensing method based on a LASER sensor, two contact sensors, and an angle sensor is proposed to implement multiple functions such as tracking the welding arc length, identifying corrugation shapes, and detecting welding gun posture. Based on the devised tracking sensor system and welding robot, a servo-control system with a surface-tracking welding control algorithm is established. The experimental results show that the robot system's welding speed is about 7 times that of hand welding and the welding qualification rate was 99%, significantly improving welding efficiency and quality as a critical equipment technology in the process of corrugated plate welding.

Measurement of medium-voltage AC air arc temperature and particle number density based on dual-wavelength Moiré deflection technology

AC air arcs are generated in medium-voltage (MV) power systems under the effect of harsh weather conditions, equipment aging, and high penetration of distributed generation, threatening equipment and public safety. The arc current and temperature are low due to the wide application of arc suppression devices. In this scenario, the MV AC air arc does not satisfy the local thermodynamic equilibrium (LTE) condition. In addition, the repeated arcing and extinguishing processes further complicate the arc discharge mechanism, which bring challenges in the modeling and detection of MV AC air arcs. Experimental methods are a direct and efficient approach to determine the properties of arc plasmas. In this study, a dual-wavelength Moiré deflection diagnostic system was established to determine the time evolution of the particle density and radial distribution of the temperature in an MV AC air arc without relying on the LTE assumption. The electron number density and heavy particle number density change transiently during the arc discharge process and change gradient along the radial direction. The heavy particle temperature and electron temperature were then calculated based on the measured particle number density. During the arcing stage, the temperature of the electrons exceeded that of the heavy particles significantly, and the arc deviated from LTE. Finally, the limitations of the traditional single-wavelength Moiré deflection method are analyzed. The classic single-wavelength Moiré deflection method, while capable of estimating heavy particle temperature in plasma, exhibits a significant error in electron density estimation compared to the dual-wavelength Moiré deflection method.

Heavy Metal Bioaccumulation in Rabbit Organs and Chrysomya albiceps (Wiedemann, 1819) Larvae: Implications for Forensic Entomology

Background: A closer relationship has been established between entomology and toxicology, giving rise to a new field known as entomotoxicology, which focuses on the bioaccumulation of toxic substances in scavenging insects and other arthropods. Methods: This study investigates the impact of lethal doses of Mercury Chloride (HgCl2) and Cadmium Chloride (CdCl2) administered to male rabbits (Oryctolagus cuniculus Linnaeus) on the distribution of Mercury and Cadmium in rabbit organs and their subsequent accumulation in Chrysomya albiceps larvae. The experimental groups were subjected to oral administration of specific concentrations of HgCl2 and CdCl2, while a control group received distilled water. Organ dissection and subsequent larval feeding were followed by acid digestion for sample preparation and inductively coupled plasma torch spectrometry coupled with a mass spectrometer (ICP-MS) was employed for analysis. Result: Results indicate a significant increase in Mercury concentrations in treated rabbit organs, with the liver exhibiting the highest concentration. Cadmium showed diverse distribution among rabbit organs, with the highest concentrations in the kidneys. Ch. albiceps larvae, reared on rabbit organs, exhibited varied concentrations of both Mercury and Cadmium, with significantly higher levels in the treated group. These findings underscore the ecological implications of heavy metal exposure and the potential utility of insect larvae in forensic investigations as bioindicators of environmental contamination.

A novel optimizing Pulsed Plasma Gas Variable Polarity Plasma Arc Welding (PPG-VPPAW) method for improving weld quality

To enhance the reliability of aluminum alloy welding quality, a novel Pulsed Plasma Gas Variable Polarity Plasma Arc Welding (PPG-VPPAW) system is proposed. This system enables independent control and rapid adjustment of the plasma gas, allowing for flexible modulation of arc pressure output under constant thermal conditions, thereby reducing porosity and refining grain structure. The research analyzed the impact of parameters of different plasma gas on arc characteristics, welding porosity, and welding microstructure. The results reveal that the periodic changes in pulsed plasma gas induce corresponding variations in arc temperature, arc shape, arc pressure, arc voltage, and the morphology of the weld pool keyhole. The magnitude of the difference between the base value and peak value of pulsed plasma gas determines the extent of arc pressure fluctuations and the behavior of the backside keyhole. The maximum oscillation amplitude of the backside keyhole can reach up to 4.5 mm². Additionally, the oscillation of pulsed plasma gas within the molten pool has been demonstrated to effectively reduce weld porosity and refine grain size. Under this process, the grain size of the weld metal can be reduced by up to approximately 25%. Current work provides an important direction for fabricating highly reliable aluminum alloy weldments.

Influence of reduced pressure on arc and weld pool properties in TIG welding

In this article, transient transport phenomena in the arc and weld pool for different ambient pressures during tungsten inert gas welding were reported. Arc plasma and weld pool behaviour vary with ambient pressure because of changes in arc thermophysical properties. The maximum arc temperature decreases with decreasing ambient pressure because of reduced plasma electrical conductivity. Decreased arc mass density results in a lower maximum weld pool surface temperature and a decrease in maximum metal vapour content as ambient pressure decreases. Arc pressure decreases with decrease in ambient pressure, resulting in shallower penetration. Calculated arc temperature distribution and weld cross-section are compared with experiments to validate the modeling method for simulating heat and mass transfer phenomena in low ambient pressure welding.

Coupling numerical simulation of plasma arc channel evolution and particle dispersion process

Arc discharge plasma (ADP) technology can be applied to disperse easily aggregated materials, such as the carbon nanotubes and Fe3O4. To investigate the evolution of the plasma arc channel and particle dispersion effect during the ADP process, a coupled electrode–plasma channel–workpiece (Fe3O4 clusters) and particle dispersion heat transfer model was established. The simulation results exhibited that the plasma arc formed at 0.05 s acted on the workpiece surface, forming a conical bottle-shaped structure with a wide arc column near the workpiece region and a narrow arc column near the electrode region due to the plasma column–workpiece interaction. With the continuous discharge, a discharge crater was formed on the workpiece surface due to the thermal-pressing effect of the plasma arc, and the dynamic pressure exerted by the arc column on the workpiece center increased continuously, driving the dispersion of the particles. In addition, ADP dispersion experiments were carried out on Fe3O4 to verify the simulation results. The experimental results showed that the morphologies of plasma arc channel evolution and discharge crater agreed with the simulation results. Moreover, the Fe3O4 particles dispersed by the ADP showed good dispersion morphology, which will further promote the spread of ADP technology in the dispersion and application of materials.

Progress of organic wastewater degradation by atmospheric pressure gliding arc plasma technology: A review

The prevention and treatment of organic pollutants in wastewater have attracted extensive attention because they threaten ecological balance and human health. Traditional wastewater treatment technologies, such as physical, chemical, biological methods, etc., are still limiting and challenging due to some factors, such as high energy consumption, chemical agents, low efficiency, and secondary pollution. At present, gliding arc plasma, based on equilibrium/non-equilibrium in plasma temperature, demonstrates itself to be one of the most promising technologies for the degradation of refractory organics with its fast degradation rates, no secondary contamination, high efficiency, and so on. The theoretical mechanisms and typical applications of gliding arc plasma degradation of wastewater are introduced in detail in this paper. The physical and chemical characteristics of gliding arc plasma and the role of the reactive species in the plasma are reviewed.

Spectral Analysis of Al Arc Discharge Plasma Generated in ZnO/DDDW Colloid

This study aims to investigate the aluminum (Al) arc plasma parameters generated through the explosive strip technique. The research involves the measurement of key plasma characteristics such as plasma frequency (fp), Debye length, and Debye number. The electron temperature (Te) and electron density (ne) of the plasma were calculated utilizing the Boltzmann plot and Stark expansion method. Analysis of the optical emission spectrum revealed distinctive peaks corresponding to oxygen, Al, and zinc oxide (ZnO) within the plasma. The outcomes of the study demonstrated a noteworthy correlation between the applied current and the electron temperature and density. Specifically, as the current increases, both electron temperature and density increase. The electron temperature of the Al plasma increased from the range of 0.852 eV to 0.92404 eV, accompanied by a corresponding elevation in electron density from 13.1× 1017 cm-3 to 15.2× 1017 cm-3. Furthermore, the detonation of the Al strip within a ZnO suspension led to even more pronounced changes. In this case, the electron temperature surged from 0.92885 eV to 1.1012 eV, and the electron density experienced an increase from 37.7 × 1017 cm-3 to 44.7 × 1017 cm-3.

Plasma-assisted pyrolysis for converting oil palm fronds into reduced graphite oxide

One of the oil palm tree’s solid waste is oil palm fronds. Due to its lignocellulosic composition, it has the potency to convert it into carbon. The common heat treatment method to convert oil palm fronds into carbon-based material is pyrolysis. However, this process has some disadvantages, such as being time-consuming and just producing amorphous carbon. Different from common pyrolysis temperatures, in this study we use a higher temperature (4000 °C) generated by DC current arc plasma. This process is faster than the common pyrolysis process (less than 10 minutes) and produces crystalline material. This product is then characterized by Raman spectroscopy, SAED-TEM, XRD, FT-IR, and SEM/EDX. Based on Raman spectroscopy, this crystalline material shows the characteristics of semiconductor carbon. Based on the SAED-TEM, there is a (002) plane of hexagonal crystal structure detected (graphite phase characteristics). An XRD analysis shows the characteristics of the trigonal crystal structure (P3) constructed by O and H atoms. An FT-IR characterization shows that there are C=C, C-H, and O-H bonds, while the EDX analysis result shows a carbon-to-oxygen ratio of about 4.23. Therefore, based on the whole interpretation, the plasma-assisted pyrolysis treatment is successfully used to convert oil palm fronds into reduced graphite oxide (rGO).

A novel magnetic field assisted powder arc additive manufacturing for Ti60 titanium alloy: Method, microstructure and mechanical properties

Due to the rapid heating-cooling process and unstable keyhole, pore defects are easily formed during the high energy beam-powder additive manufacturing (AM) process, posing great challenges to the high-performance manufacturing of aerospace components. Using an arc with lower energy density as a heat source can effectively avoid these defects, but its matching raw materials are limited to wire. In this paper, a novel magnetic field assisted powder arc additive manufacturing (MFA-PAAM) method has been proposed, which combines arc heat source and powder raw material to achieve dense metal parts. A transverse magnetic field (TMF) was introduced to solve the powder spattering problem which impacts the stability of the PAAM process, by regulating the direction of the arc plasma flow and the arc pressure. The unique melting behavior of the powder under arc heating was captured by a high-speed camera, which can be summarized into two steps: balling and adsorption by the molten pool. And the well-formed and fully dense Ti60 high-temperature titanium alloy wall components were successfully manufactured using the self-developed equipment. The microstructure of the thin-wall component is dominated by basket-weave distributed α laths and few β sheets remaining at their boundaries. A layered periodic distribution along the building direction was observed, which is mainly distinguished from the content and morphology of the β phase. The average ultimate tensile strength (UTS) and elongation to failure in the travelling direction are 1003.2 MPa and 15.1%, while the average UTS and elongation along the building direction are 1009.3 MPa and 16.6%, respectively. The fracture morphologies in both directions are characterized by ductile fracture. The MFA-PAAM technique shows great potential for fabricating materials that are difficult to be drawn into wires with high efficiency and performance.

Cutting and Shield Gases Pressure Effects on Plasma Cutting Quality

In this paper, the effects of the shield gas on cut quality in plasma arc cutting were quantified experimentally. Measurements were performed on plasma arc cutting kerfs (PACs) cut through a 4 mm (1/8 in.) S355 steel plates with a Gys Neocut105 cutter equipped with a Toparc AT-125 torch. This system uses compressed air as both cutting and shield gas. Separate circuits for shielding air and cutting air were used. This way, the influences of the shield air and the cutting air could be studied independently. A full 3-factor, 3-level Taguchi design was followed. The studied factors are the cutting air pressure, the shield air pressure, and the arc current. The measured responses are the removed steel surface and the right and left bevel angles. As expected, the current proved to have the greatest influence on the kerf surface. The cutting air pressure significantly influenced the kerfs’ shapes while the shield air flow rate proved less important yet sensitive. Some negative bevel angles at high plasma, high cutting, and high shield air pressures have also been observed.

Prototype of Laboratory-Scale Plasma Arc for Thin Film Growth and Its Testing

Prototype of Laboratory-Scale Plasma Arc for Thin Film Growth and Its Testing

Electromagnetic–Computational Fluid Dynamics Couplings in Tungsten Inert Gas Welding Processes—Development of a New Linearization Procedure for the Joule Production Term

The finite volume method (FVM) was used to model a tungsten inert gas (TIG) arc welding process. A two-dimensional axisymmetric model of arc plasma integrating fluid–solid coupling was developed by solving electromagnetic and thermal equations in both the gas domain and the solid cathode. In addition, two additional coupling equations were considered in the gaseous domain where the arc is generated. This model also included the actual geometry of torch components such as the gas diffuser, the nozzle, and the electrode. The model was assessed using numerous numerical examples related to the prediction of the argon plasma mass fraction, temperature distribution, velocity fields, pressure, and electric potential in the plasma. A new linearization method was developed for the source term in the energy conservation equation, allowing for the prediction of Joule effects without artificial conductibility. This new method enhances the efficiency of the classical approach used in the literature.

Experimental study on the life and performance of an improved DC arc plasma torch

A novel DC arc plasma torch is designed in this paper in order to reduce the electrode erosion, and a series of experiments are carried out to investigate how to improve the lifetime and performance of the nitrogen DC arc plasma torch. The analysis of voltage characteristics of the plasma torch indicates that the interelectrode insert can increase the average arc voltage and the sudden expansion structure can reduce the voltage fluctuation, which is helpful to improve the working stability to some extent. The spectrum characteristics at the plasma torch outlet and the cold flow simulations show that the dual shielding gas mainly act near the anode and can effectively cover the entire anode wall. Combining the shielding gas distribution with anode heat transfer processes in argon and nitrogen plasma torch, it is inferred that argon shielding gas plays an important role on reducing the anode heat transfer processes in nitrogen plasma torch, which can effectively suppress the anode erosion. The life testing experimental results find that there is no significant erosion of the cathode, anode, and interelectrode insert after cumulative working time exceeding 20 h. The maximum nitrogen plasma jet length can reach ∼35 mm with the outlet jet temperature of about 20 000 K at the current of 100 A and nitrogen gas flow rate of 10 slm. The maximum average specific enthalpy and thermal efficiency are respectively about 14 MJ kg−1 and 75% in the nitrogen plasma torch. Therefore, this newly designed DC arc plasma torch not only can suppress the electrode erosion but also has good working performance, which is expected to have excellent application prospects.

Microwave Exfoliated Graphene Oxide for Sorption Concentration of Gold and Silver

A method has been reported for determining of Au and Ag in waters using preliminary sorption concentration of these analytes by microwave exfoliated graphene oxide (GO) and quantitative analysis by two-jet arc plasma atomic emission spectrometry (TJP-AES) and graphite furnace atomic absorption spectrometry (GFAAS). The parameters of sorption of analytes such as duration of sorption and pH were optimized for the preliminary concentration of Au and Ag on various carbon sorbents for subsequent TJP-AES and GFAAS analysis. The sorption properties of carbon nanotubes (CNTs), multilayer graphene (MLG) and GO such as sorption capacity and surface area were compared. The content of analytes in sorption materials was defined. The results demonstrated that GO provides the best sorption properties and the use of exfoliated GO for preconcentration decreaces the blank signal from nonselective absorption by 10 to 120 times. The limits of detection (LODs) for Au and Ag are 4·10−1 µg L−1 and 8·10−2 µg L−1 by GFAAS and 5 µg L−1 and 2·10−1 µg L−1 by TJP-AES.

Review of DC and AC Arc Plasma at High Pressures Above Atmospheric Pressure

Review of DC and AC Arc Plasma at High Pressures Above Atmospheric Pressure

Formation and strengthening mechanism of equiaxial cellular grain zone in AA2195-T8 Al–Cu–Li alloy twin-wire P-VPPA welded joint with Ti–Zr microalloying

A novel method involving twin-wire pulsed VPPA (P-VPPA) welding was combined with Ti–Zr microalloying to improve the mechanical properties of AA2195-T8 Al–Cu–Li alloy variable polarity plasma arc (VPPA) welded joints. This method aimed to increase the width of the equiaxial cellular grain zone (ECZ) by adding higher content of Ti–Zr and reducing heat input. The microstructure evolution process was established to understand the formation and strengthening mechanism of the ECZ. The results showed that the strength of the ECZ was higher than that of the dendrite in the weld zone (WZ). The twin-wire VPPA welding led to the formation of a wider ECZ near the fusion zone (FZ). This ECZ was continuously distributed throughout the thickness direction of the welded joint. Combined with higher Ti–Zr microalloying, the maximum width of ECZ increased to 2.5 mm and extended to the WZ. Consequently, the proportion of cracks passing through the ECZ during tensile fracture increased from 27.6% to 88.7%. Moreover, the ultimate tensile strength (UTS) of the welded joint exhibited a notable improvement, rising from 328 MPa to 370 MPa, while the elongation also increased to 5%. The UTS of the welded joint achieved 66% of the base metal. Additionally, the average grain size in the ECZ was 14 μm. The formation of the ECZ was primarily attributed to the nucleation precursors of Al3(Ti, Zr) and β′ phase, as well as less welding heat input near the FZ. The widening of the ECZ was mainly due to the presence of more Al3(Ti, Zr) phases. Moreover, the grain boundary of the ECZ exhibited the distribution of Al–Cu eutectic, θ(Al2Cu), Ω, T2(Al6CuLi3), and ω(Al7Cu2Fe) phases, while a small amount of T1(Al2CuLi) phase precipitated within the grain. The strengthening mechanism of ECZ is the result of multiple strengthening effects, including the reduction of element segregation and microcracks, the precipitation of the T1 phase, and the fine grain strengthening.

Adhesion characteristics of plasma-treated flax fabrics and elastoplastic properties of their biocomposites

ABSTRACT Recently, there has been growing interest in replacing synthetic fibers with natural fibers in polymer composites due to several advantages of natural fibers over synthetic ones, such as low cost, low density, sustainability, and biodegradability. However, a significant drawback of natural fibers is their high capillary water absorption, worsened by waxes and atmospheric pollutants, resulting in weak adhesion with polymer matrices. Surface treatments, including plasma treatments, have shown promise in improving this interfacial bonding. In this study, woven flax fabrics (FFs) were treated with two plasma techniques: atmospheric pressure plasma torch (APPT) and low-pressure plasma (LPP). The plasma effects on the fibers’ surface, wettability, and surface energy were assessed through X-ray photoelectron spectroscopy and contact angle measurements, respectively. Subsequently, the treated fibers were utilized to fabricate biopolymer composites using polyamide1 (PA11), green low-density polyethylene (GPE), and polybutylene succinate (PBS) as matrices. The adhesion strength and elastoplastic behavior of the biocomposites were compared by peel-off test and plasticity index measurement. The results indicated that both treatments successfully improved the FFs’ surface characteristics, resulting in increased wettability and surface energy. The higher peeling strengths and lower plasticity indices confirmed the improvement in the adhesion of treated FFs with the biopolymer matrices.

Impact of motile microorganisms on a Sutterby nanofluid flow over a rotating disk with Hall current and ion slip

The dynamics of partly ionized fluid flow, when subjected to a magnetic field, differ considerably from that of typical fluid flow. The main applications of the partially ionized fluids including thermal arc plasma cutting, gas discharge lamps, lighting, and plasma medicine have made them vital when discussed under the effects of the applied magnetic field. This study discusses the flow of the Sutterby nanofluid over a stretching disk with Hall and ion slip effects amalgamated with Cattaneo–Christov double diffusion. The uniqueness of the envisaged model is enriched by considering the gyrotactic microorganisms. The system of governing equations is normalized and addressed numerically by applying the bvp4c package of MATLAB software. The outcomes are depicted via graphs and in tabularized form. It is perceived that fluid velocity is affected by the Hall current parameter. For the bioconvection Lewis number, a decline in the microorganism distribution is also observed. In addition, it is also perceived that the fluid concentration is enhanced against mass diffusion relaxation stress. The validity of the envisioned model by comparing it with a published study is also a part of this exploration.