Anode Plasma Research Articles

Capping agent-free aqueous gold nanoparticles generated by an environmentally friendly plasma-liquid method

This study investigates a simple approach for synthesizing gold nanoparticles (Au NPs) using atmospheric pressure plasma without the need for reducing agents, additives, or capping agents. The size, morphology, optical properties, and aggregation stability of the synthesized Au NPs were characterized using scanning electron microscopy, UV-vis spectroscopy, and zeta potential analysis. The UV-vis absorption spectra of the gold nanoparticles, obtained at various Au3+ concentrations and treatment durations with anode plasma discharge, were analyzed. The UV-vis spectra revealed a surface plasmon resonance absorption band between 530–600 nm, indicative of Au NP formation. Results demonstrated that the size of Au NPs can be tuned within the range of 30–75 nm by adjusting the gold salt precursor concentration from 0.3 to 2.5 mmol/L. It was found that plasma treatment for 3–10 minutes, at different Au3+ concentrations, resulted in the formation of Au NPs with varying sizes and morphologies. The study showed that particles with different shapes – spherical, hexagonal, and triangular – were formed depending on the initial concentration of Au3+. The plasma-chemically synthesized nanoparticles at an Au3+ concentration of 0.06 mmol/L were predominantly spherical and exhibited the highest stability (lasting 12–24 hours), with a zeta potential of –20 to –22 mV, compared to samples with Au3+ concentrations ranging from 0.3 to 2.5 mmol/L.

Spoke-Type Structures in an Ion Diode with Magnetic Insulation of Electrons

The article presents the results concerning the cross-sectional energy density distribution of a pulsed ion beam for two types of diodes with electron open drift: with external magnetic insulation (250 kV, 80 ns, 0.6 T) and with self-magnetic insulation of electrons (250–300 kV, 120 ns, 0.8 T). Anode plasma is formed using a breakdown along the surface of the anode dielectric coating (single-pulse mode) or explosive electron emission (with double opposite-polarity pulses). It was found that, when the energy density of the ion beam exceeds ≈0.4 J/cm2, periodic spoke-type structures with a step of 3–6 cm in the beam cross section are formed. The processes of formation of such a structure—nonuniform density of anode plasma and self-organization of anode and/or cathode plasma in crossed electric and magnetic fields—are analyzed. It is shown that the formation of local plasma regions in the anode–cathode gap of an ion diode can cause the formation of a periodic structure of the cross-sectional energy density distribution.

Effects of anode evaporation process on the anode sheath characteristics in vacuum arc plasma

Abstract The anode sheath of vacuum arc plasma plays a key role in the generation of anode plasma, but the effects of anode evaporation on the anode sheath remains unclear. In this paper, a theoretical model of a collisional sheath for multi-component plasma coupled with anode evaporation is developed, and the spatial evolution of the anode sheath at different anode surface temperatures is investigated. The results indicate that the distribution of charged particles density and potential in the anode sheath monotonically decreases in the absence or reduction of anode evaporation. When the anode surface temperature exceeds 1900K, a potential hump appears within the sheath. This is due to enhanced anode evaporation increasing the metal vapor density, which intensifies electron impact ionization and charge exchange collisions, resulting in a higher net space charge density. Finally, the effects of various collision reactions and electron temperatures on the potential hump are analyzed. These findings are meaningful for understanding the anode plasma generation mechanism and regulating the anode plasma parameters.

CATHODIC AND ANODIC PLASMA ELECTROLYSIS ON NITRATE SYNTHESIS

Nitrogen fixation using plasma electrolysis is an alternative in the production of liquid nitrate fertilizer which is safe for the environment because it does not produce emissions that pollute the environment. The effectiveness of nitrate production is shown from the position of plasma formation at cathodic and anodic levels. This study aims to analyze the comparison of cathodic and anodic plasma electrolysis levels in producing nitrate. Current-voltage characterization is carried out to determine the position of plasma formation. The glow discharge of the cathodic plasma is achieved after the critical voltage (280 V) is lower than that of the anodic plasma (650 V). Measurement of emission intensity using electron spin resonance to determine reactive species that play a role in the formation of nitrate in cathodic and anodic plasma. Nitrate formation is influenced by reactive species in the form of N, N2*, N2+, •OH, •H and •O, especially reactive species of nitrogen and •OH are needed to form nitrate both from the NO pathway (anodic plasma) and from the ammonia pathway (cathodic plasma). The results of this study showed that anodic plasma electrolysis was more effective for nitrate synthesis. Nitrate produced from anodic plasma is 1889 mg L-1, greater than cathodic plasma as much as 213 mg L-1.

Complex electron-ion-plasma surface modification of high-alloy stainless steel

The work is devoted to identification and analysis of patterns of change in the elemental and phase composition, defective substructure, mecha­nical (microhardness) and tribological (wear resistance and friction coefficient) properties of stainless high-chromium steel subjected to complex processing, combining vacuum irradiation of the samples surface layer with an intense pulsed electron beam of submillisecond exposure duration and subsequent nitriding under electron-ionic heating conditions. High-chromium steel AISI 310S, which in the initial state is a polycrystalline aggregate based on γ-iron, was used as the research material. Pulsed electron beam treatment of steel was carried out on a “SOLO” installation equipped with an electron source with a plasma cathode based on a low-pressure pulsed arc discharge with grid stabilization of the cathode plasma boundary and an open anode plasma boundary. Steel nitriding was carried out on a “TRIO” installation with a chamber size of 600×600×600 mm, equipped with a switching unit to implement the electron-ionic processing mode. Nitriding was carried out at 723, 793, and 873 K temperatures for 1, 3 and 5 h. It was found that electron-ionic nitriding of the samples pre-irradiated with an electron beam (10 J/cm2, 200 μs, 3 pulses at 723 and 793 K for 3 h) is accompanied by the formation of a ceramic layer containing only iron and chromium nitrides. The highest values of steel wear resistance after electron-ionic nitriding, exceeding the wear resistance of the initial steel by more than 700 times, are observed at nitriding parameters of 793 K, 3 h.

Influence of Elements in Steel With Anode Plasma Electrolytic Boriding on Hardness Gradient and Tribological Properties

Abstract The influence of elements in steel on anode plasma electrolytic boriding has been studied. The modified layers and surfaces on steel samples were analyzed by a scanning electron microscope, an X-ray diffractometer, a surface profiler, a microhardness tester, and a ball-disc tribometer. With 1045 steel as the control group, the same treatment parameters (treatment with 5 min, 200 V of voltage, 5% boric acid, and 10% ammonium chloride) were implemented on various steel substrates. It was found that a low content of carbon would hinder the penetration of boron, and other metallic elements can improve the mircrohardness gradient and decrease the wear-rate. Chromium and manganese can increase the maximum microhardness than treated 1045 by about 15%, but have a detrimental effect on surface flatness. Nevertheless, manganese has the ability to rapidly create a layer of oxide that enhances the tribological characteristics, leading to a remarkably low average friction coefficient of 0.26 for 1046 steel. The presence of molybdenum in the element composition of 4140 steel results in a notable enhancement of surface properties, namely in terms of wear resistance, with a minimum wear-rate 2.1 × 10−6 g/Nm for 4140 steel. Nickel does not appear to have a notable impact on the surface characteristics of the modified samples.

Performance improvement studies of axially partitioned dual band magnetically insulated line oscillator

In magnetically insulated line oscillator (MILO)s, a proportion of device current is responsible for the self-generated magnetic field that aids electron flow confinement in the anode cathode gap, thereby suitable RF generation. The device currents should not be high due to its direct impact on device efficiency, and electron energy depositions at load can lead to anode plasma formation. Also, the lower currents can facilitate the device to operate at larger voltages and/or for longer operational times. In this article, couple of axially partitioned dual band MILOs (DBMILO) designs that operate at lower device currents in comparison with the existing axially partitioned DBMILOs in the literature is presented. For one design with the radius of the slow wave structure (SWS), i.e., RSWS = 40 mm, the injection of the DC electron beam parameters 505 kV and 49 kA, generated an output RF power of ∼5.8 GW oscillating at 3.71 and 10.16 GHz (S-and X- bands) concurrently with ∼23.8% conversion efficiency. However, the other design (RSWS = 40.6 mm) at beam voltage 505 kV and device current of 47 kA generated an output RF power of >3.85 GW oscillating at 3.5 and 10.5 GHz, concurrently, where the frequencies are harmonically related. Thus, the proposed designs yielded significant device current reduction to ∼47 and ∼49 kA from ∼56 kA (existed), respectively, thereby drop of 16% and 12.5% to its counter designs, respectively. Also, there is substantial reduction in the electron energy depositions, thus the occurrence of anode plasma formations. Moreover, the peak conversion efficiency is enhanced to 23.4% and 16.4%, from 12.8%.

Recent advancements in the surface treatments for enhanced biocompatibility and corrosion resistance of titanium-based biomedical implants

Titanium-based biomedical implants are widely used owing to their biocompatibility, corrosion resistance and mechanical strength. Although, they still face challenges such as poor osseointegration and implant failure caused by corrosion. To address these challenges, various surface treatments have emerged to enhance the biocompatibility and corrosion resistance of titanium implants. This review article presents a concise overview of the innovative surface treatments for enhanced corrosion resistance and biocompatibility of titanium-based biomedical implants. The surface treatment briefly discussed includes physical, chemical, and biological treatments, such as plasma spraying, anodization, electrochemical deposition, and biomimetic coating. Furthermore, this article also highlights the importance of surface treatments to enhance the biological performance of titanium-based implants. This review provides insights for researchers and clinicians in the field of titanium-based biomaterials and may contribute to the development of more effective and durable biomedical implants.

Cathode spot dynamics in axial magnetic fields

Cathodic arcs (CA) are important across a wide range of applications including thin film deposition and solid fuel space propulsion. Understanding how cathode spots (CSs) move in magnetic fields has important implications for the deposition rates and thrust delivered as well as cathode/fuel usage efficiency. In this work, we investigated the dynamics of cathode spot (CS) motion in the presence of various axial magnetic fields (AMFs) in a high-current multi-spot CA system. Two photography techniques were used (i) long exposure and (ii) high-speed framing photography. The long-exposure images of cathode spots suggested that the cathode spots do not travel in spiral paths produced by Robson drift, as observed in previous vacuum interrupter system experiments. The reduced prevalence of Robson drift was found to be insufficiently explained considering only anodic plasma emission difference arising from the annular anode geometrical setup. High-speed framing images of cathode spots during discharges revealed a statistically significant reduction of the speed of cathode spot motion, as characterized by a decrease in K value as the applied AMF increases.

Anodization and Plasma Electrolytic Oxidation Treatments of AZ91D Mg Alloy in Alkaline Aqueous Solutions

Mg alloys, such as AZ91 (Mg-9mass%Al-1mass%Zn), are lightweight materials with excellent mechanical properties. The applications of Mg alloys in automobiles could significantly contribute to reducing carbon dioxide emissions. Mg alloys are fully recyclable and abundantly available, which increases their desirability in light of rising environmental consciousness. However, the low corrosion resistance of Mg alloys is one of the major limitations to further applications.In Mg alloys, corrosion behavior is known to be related to the microstructure. During the real-time in situ observation of the corrosion process under galvanostatic polarization, filiform corrosion proceeded along the outside of the β phase (in lamellar α + β microstructure and along the α-mother phase 1. Furthermore, the β phase exhibited a higher potential in the OCPs of each phase and a small area with the boundary in 0.1 M NaCl at pH 8.0 2. Thus, the surface films of β phases was thought to suppress the corrosion of Mg alloys. Mg alloys can be treated by anodic oxidation or plasma electrolytic oxidation to obtain excellent corrosion resistance. The latter is similar to anodic oxidation but applies a higher voltage, which causes a discharge on the electrode surface and the resulting plasma modifies the oxide film significantly.In this study, anodic oxidation and plasma electrolytic oxidation were performed on AZ91D Mg alloy in alkaline solutions such as sodium phosphate. This study aims to compare the two methods in the same solution and to produce an Al-rich surface film with excellent corrosion resistance.In anodic oxidation, the size of the electrode area was approximately 1 cm2. The surface of the specimen was coated with epoxy resin, followed by paraffin. The reference electrode was Ag / AgCl (3.33 M KCl). The experiments were performed at 25 ℃. The scan rate of potentiodynamic polarization was set at 23 mV min-1. The starting potential was set at 20 mV lower than the open-circuit potential. The anodic oxidation treatments were terminated at 0 V, 3 V, and 5 V. Plasma electrolytic oxidation was performed with a liquid volume of 500 mL. The sample was mounted on a resin holder. The electrode surface was approximately 50 mm2. A Pt plate was used as the counter electrode. The sample and the counter electrode were fixed at a distance of 0.5 cm. A plasma-generating power supply was used. The solution was cooled down to 20 ℃ while the voltage was applied. The frequency and the pulse interval were adjusted. The voltage and type of solution were changed to produce the film. Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Corrosion Science, 192, 109834 (2021).Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Journal of Magnesium and Alloys, 11, 137-153 (2023).

Fixation of air nitrogen to ammonia and nitrate using cathodic plasma and anodic plasma in the air plasma electrolysis method

AbstractThe fixation of nitrogen (N2) from the air into ammonia (NH3) and nitrate (NO3−) is usually conducted using the Haber–Bosch process, which requires the raw material of hydrocarbons for hydrogen (H2), which has a large amount of energy but produces high CO2 emissions. An environmentally friendly and energy‐saving alternative is the air plasma electrolysis method, which can be used to synthesize NH3 and NO3− under ambient conditions. In this study, this method was used to inject air into the plasma zone in a K2SO4 electrolyte solution to produce N2 fixation compounds. The results showed that the use of cathodic plasma promoted the formation of NH3 but suppressed NO3− production. The optimal air injection rate was achieved at 0.6 L.min−1 and an electrical power of 452 W, with a total fixed N2 of 51.66 mmol. The highest formation of NO3− in cathodic plasma was obtained in 35 min, with a value of 29.92 mmol, and 2.57 mmol NH3 was achieved at 60 min. The high concentration of H2 gas, which is a by‐product of this process, can contribute to increasing the use of Haber–Bosch green technology in the production of NH3.

Influence of Anode and Cathode Plasmas on the Operation of an Electronic Diode with an Explosive-Emission Cathode

Influence of Anode and Cathode Plasmas on the Operation of an Electronic Diode with an Explosive-Emission Cathode

Obtaining thin film semiconductor oxides by stimulated plasma anodizing technology and their studying

Obtaining thin film semiconductor oxides by stimulated plasma anodizing technology and their studying

Improved Tribocorrosion Properties of Ti6Al4V Alloy by Anodic Plasma Electrolytic Oxidation

Ti6Al4V alloy has good corrosion resistance due to the formation of the passive oxide films on the surface of Ti6Al4V alloy. However, Ti6Al4V alloy has poor tribocorrosion resistance in the seawater environment. Herein the present work, plasma electrolytic oxidation (PEO) with the electrolyte of glycerol and sodium borate is used to generate PEO coatings on the surface of Ti6Al4V alloy to improve its tribocorrosion properties. The microstructure and tribocorrosion properties of PEO coatings are investigated by using scanning electron microscopy, X‐ray diffraction, and tribometer, respectively. The growth kinetics and the tribocorrosion mechanisms of PEO coatings are discussed in detail. It is shown in the results that PEO coatings deposited on the surface of Ti6Al4V alloy are composed of rutile and anatase phases. The surface hardness and thickness of PEO coatings are enhanced with the increase of the voltage and time. The wear rate of Ti6Al4V alloy with PEO coatings is significantly reduced in artificial seawater.

PLASMA-ELECTROLYTIC MODIFICATION OF STEEL AND TITANIUM SURFACES BY COMBINING CATHODIC NI-TRIDING AND ANODIC POLISHING

The possibility of increasing the wear resistance of steel 45 surfaces by 19.9 times and titanium alloy VT6 by 3.6 times after cathodic electrolytic plasma nitriding in a solution of ammonium chloride and ammonia and subsequent anodic electrolyte-plasma polishing in a solution of ammonium sulfate. A positive effect on wear resistance was revealed reducing surface roughness and removing the outer part of the oxide layer using anodic electrolytic plasma polishing and increasing the hardness of the surface layer as a result of cathodic nitriding. The wear mechanism is defined as fatigue upon plastic contact and boundary friction.

Effects of anode material on the evolution of anode plasma and characteristics of intense electron beam diode

In this paper, three kinds of materials including graphite, titanium (Ti) and molybdenum (Mo) are used as anodes to figure out the influence factors of anode material on the characteristics of the intense electron beam diode. The results show that the characteristics of diode are mainly determined by the cathode plasma motion under a 15 mm diode gap, in which the typical electron beam parameters are 280 kV, 3.5 kA. When the diode gap is reduced to 5 mm, the voltage of the electron beam reduces to about 200 kV, and its current increases to more than 8.2 kA. It is calculated that the surface temperatures of Ti and Mo anodes are higher than their melting points. The diode plasma luminescence images show that Ti and Mo anodes produce plasmas soon after the bombardment of electron beams. Ti and Mo lines are respectively found in the plasma composition of Ti and Mo anode diodes. Surface melting traces are also observed on Ti and Mo anodes by comparing the micromorphologies before and after bombardment of the electron beam. These results suggest that the time of anode plasma generation is closely related to the anode material. Compared with graphite, metal Ti and Mo anodes are more likely to produce large amounts of plasma due to their more significant temperature rise effect. According to the moment that anode plasma begins to generate, the average expansion velocities of cathode and anode plasma are estimated by fitting the improved space-charge limited flow model. This reveals that generation and motion of the anode plasma significantly affect the characteristics of intense electron beam diode.

Increasing the Hardness and Wear Resistance of Commercial-Purity Titanium by Anodic Plasma Electrolytic Carburizing

Increasing the Hardness and Wear Resistance of Commercial-Purity Titanium by Anodic Plasma Electrolytic Carburizing

Increasing Hardness and Wear Resistance of Austenitic Stainless Steel Surface by Anodic Plasma Electrolytic Treatment

The results of modifying the surface of austenitic stainless steel by anodic plasma electrolytic treatment are presented. Surface treatment was carried out in aqueous electrolytes based on ammonium chloride (10%) with the addition of ammonia (5%) as a source of nitrogen (for nitriding), boric acid (3%) as a source of boron (for boriding) or glycerin (10%) as a carbon source (for carburizing). Morphology, surface roughness, phase composition and microhardness of the diffusion layers in addition to the tribological properties were studied. The influence of physicochemical processes during the anodic treatment of the features of the formation of the modified surface and its operational properties are shown. The study revealed the smoothing of irregularities and the reduction in surface roughness during anodic plasma electrolytic treatment due to electrochemical dissolution. An increase in the hardness of the nitrided layers to 1450 HV with a thickness of up to 20–25 μm was found due to the formation of iron nitrides and iron-chromium carbides with a 3.7-fold decrease in roughness accompanied by an increase in wear resistance by 2 orders. The carburizing of the steel surface leads to a smaller increase in hardness (up to 700 HV) but a greater thickness of the hardened layer (up to 80 μm) due to the formation of chromium carbides and a solid solution of carbon. The roughness and wear resistance of the carburized surface change are approximately the same values as after nitriding. As a result of the boriding of the austenitic stainless steel, there is no hardening of the surface, but, at the same time, there is a decrease in roughness and an increase in wear resistance on the surface. It has been established that frictional bonds in the friction process are destroyed after all types of processing as a result of the plastic displacement of the counter body material. The type of wear can be characterized as fatigue wear with boundary friction and plastic contact. The correlation of the friction coefficient with the Kragelsky–Kombalov criterion, a generalized dimensionless criterion of surface roughness, is shown.

Improved Wear Resistance of Low Carbon Steel by Duplex Surface Treatment Combining Cathodic Plasma Electrolytic Nitrocarburising and Anodic Plasma Electrolytic Polishing

Improved Wear Resistance of Low Carbon Steel by Duplex Surface Treatment Combining Cathodic Plasma Electrolytic Nitrocarburising and Anodic Plasma Electrolytic Polishing

Formation of Anode Plasma in an Electron Diode with an Explosive-Emission Cathode

Formation of Anode Plasma in an Electron Diode with an Explosive-Emission Cathode