Search Results (651)

The effect of treatment time on arc-enhanced glow discharge plasma-assisted nitriding (AEGD-PAN) of AISI M2 high-speed steel was investigated for non-heat-treated and heat-treated substrates. Nitriding treatments were carried out at 350 °C for 1.5 and 3.5 h, producing diffusion layers with thicknesses ranging from approximately 38 to 75 µm without formation of a continuous brittle compound layer. X-ray diffraction combined with Rietveld refinement revealed the progressive formation of γ′-Fe₄N and ε-Fe₂₃N nitrides together with lattice expansion of the α-Fe matrix, indicating nitrogen supersaturation and precipitation strengthening within the diffusion zone. Heat-treated specimens exhibited higher surface hardness, reaching ~1350 HV_0.1, while non-heat-treated substrates developed pronounced hardness gradients associated with diffusion-controlled layer growth. Scratch testing showed improved resistance to contact-induced damage with increasing nitriding time, particularly for the 3.5 h treatment, where lateral cracking was significantly reduced and load-bearing capacity increased. Multi-pass scratch wear tests revealed a reduction in the Archard wear coefficient by up to four orders of magnitude compared with untreated M2 steel. These results demonstrate that AEGD-PAN at moderate temperature enables efficient diffusion layer formation and significant improvement in the tribological performance of high-alloy tool steels. Full article

Wire arc additive manufacturing (WAAM) is an efficient, low-cost technique for fabricating large-scale metallic components and, in particular, functionally graded materials (FGMs). This review focuses on the fabrication of 316L stainless steel–Inconel 625 FGMs by arc-based WAAM processes, examining Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW) in terms of their microstructural outcomes, compositional control strategies, residual stress development and mechanical performance. A critical finding emerging from the reviewed literature is that direct compositional interfaces between 316L and Inconel 625 can yield superior tensile strength and ductility and lower residual stresses compared to smooth gradient strategies, owing to the formation of detrimental secondary phases such as δ-phase, Laves phase and MC carbides at intermediate iron–nickel compositions encountered only during graded builds. The potential of Submerged Arc Additive Manufacturing (SAAM) as a future high-deposition-rate alternative for large-scale FGM fabrication is also discussed. Key challenges, including dilution control, Laves phase formation, residual stress management and the corrosion characterization of the graded region, are identified, together with priority research directions for advancing the industrial adoption of arc-based FGM components. Full article

Modern dentistry increasingly relies on light-curing units (LCUs) and lasers in essential clinical procedures such as composite resin polymerization, caries treatment, and periodontal therapy. This review aims to outline the evolution of light-emitting technologies and to assess their potential biological risks, with particular emphasis on effects on the visual system, oral tissues, and microbiome. The development of curing devices is presented chronologically, from the first-generation ultraviolet (UV-A) lamps introduced in the 1970s to current light-emitting diode (LED-LCU) systems and dental lasers (e.g., Er:YAG, Nd:YAG). The progressive increase in light intensity—now exceeding 3000 mW/cm²—has shortened curing times but simultaneously raised safety concerns. Major hazards include the so-called blue-light hazard, where exposure to high-energy visible (HEV) blue light may accelerate macular degeneration, and temperature elevations in the pulp chamber, which may damage the dentin–pulp complex. Laser radiation also exerts significant microbiological effects: Er:YAG and diode lasers demonstrate bactericidal activity against biofilms and oral pathogens (e.g., P. gingivalis), although therapeutic outcomes depend on wavelength, dose, and exposure time. Suboptimal parameters may lead to microbiome disturbances, whereas low-level laser therapy (LLLT; 600–1200 nm) supports tissue regeneration and helps restore microbial balance. The individualization of irradiation parameters, combined with thorough theoretical knowledge, operator expertise, and technical understanding of LCUs and lasers, is essential for maximizing clinical benefits while minimizing health risks and preserving oral microbiome homeostasis. Full article

The design and main parameters of a plasma–chemical reactor containing two compartments are presented. One compartment houses a vacuum-arc evaporator, while the other houses a planar magnetron. The compartments are separated by a diaphragm with a dosing slot for injecting copper vapor into the TiN synthesis compartment. The conditions for the synthesis of superhard TiN-Cu composite coatings are experimentally determined. Based on established process parameters for TiN synthesis in a nitrogen-containing plasma by Ti evaporation using a vacuum-arc discharge, it is proposed to apply TiN-Cu coatings by injecting Cu vapor into the TiN synthesis area and sputtering Cu using a magnetron discharge. XRD analyses of both TiN and TiN-Cu coatings show the presence of WC, Ti₂C, and TiN. EDS analysis confirms 5.57 at. % copper on the surface of the TiN-Cu coating. Real-life operating tests of TiN-Cu coatings on replaceable WC-TiC-Co (79/15/6 wt.%) alloy hexagonal inserts used for cutting 40Kh steel revealed that applying the TiN-Cu coating extends the tool life of WC-TiC-Co inserts by about 2.5 times compared with uncoated tools. Cutting force measurements on TiN-Cu-coated inserts showed no vibration or noise during cutting, driven by a reduced friction coefficient and improved heat dissipation at the contact zone between the cutting edge and the workpiece, thereby lowering the temperature in that area. Full article

This paper presents the results of studies on the synthesis of nitrogen oxides (NOx) in a three-phase GlidArc plasma reactor operating at atmospheric pressure. The objective was to determine the influence of electrical power and gas flow rate on NOx concentration, process productivity, and energy efficiency. The analysis was performed over a wide range of power levels and air flow rates, using global energy efficiency (GEE), specific energy consumption (E), and specific energy input (SEI) as evaluation metrics. The results demonstrate that discharge intensification initially leads to an increase in NOx concentration; however, at higher power levels a deterioration of energy efficiency is observed due to increasing thermal losses and partial destruction of nitrogen oxides. Gas flow rate was also found to play a significant role by determining the gas residence time in the plasma zone and the degree of reactant conversion. Based on the analysis of the median GEE and E maps, a recommended operating window for the reactor was identified, within which high energy efficiency and high NOx productivity are simultaneously achieved. The obtained results provide a basis for further optimization and scaling of GlidArc technology in the context of decentralized nitrogen compound production. Full article

Controlling carbon dioxide (CO₂) emissions remains a central challenge in Indonesia’s energy transition and its commitment to achieving net-zero emission targets. Carbon Capture and Storage (CCS) and Carbon Capture, Utilization, and Storage (CCUS) are widely recognized as important mitigation pathways, particularly for energy and industrial sectors where rapid decarbonization remains difficult. In parallel, cold plasma technology has emerged in the recent scientific literature as an early-stage, non-thermal approach for CO₂ activation under relatively low bulk temperature conditions, attracting interest as a potential long-term research pathway. This paper examines cold plasma technology within the broader CCS/CCUS landscape in Indonesia from a policy and technology perspective. The study adopts a qualitative and descriptive approach, synthesizing the selected academic literature on plasma-based CO₂ conversion, global CCUS development trends, and Indonesia’s regulatory, infrastructural, and energy system context. Rather than assessing techno-economic feasibility, the analysis focuses on identifying structural constraints, performance trade-offs, and policy-relevant considerations. The findings indicate that across plasma configurations, including dielectric barrier discharge, gliding arc, microwave, and radio frequency plasmas, current research outcomes remain constrained by low energy efficiency, limited scalability, and low technology readiness for large-scale applications. Reported performance metrics are largely derived from laboratory-scale studies under controlled conditions and cannot yet be extrapolated to real-world emission sources without a comprehensive system-level evaluation. Compared with established CCS and CCUS pathways, cold plasma technologies remain exploratory and lack the maturity required for near-term deployment. From a policy and research perspective, cold plasma should therefore be regarded as a long-term research option rather than an implementable mitigation solution for Indonesia, with its potential contribution lying in informing future research agendas, technology monitoring, and innovation planning, particularly in relation to CO₂ utilization concepts and decentralized energy systems, contingent upon significant advances in energy performance, system integration, and standardized evaluation frameworks. Full article

Nanostructured products synthesized using electric arc vapor plasma with various alcohol solutions exhibiting very high enthalpy and low mass flow rates in a direct current discharge in direct contact with a vapor vortex surrounding the arc column were studied. The nanostructured products obtained in our experiments with various alcohol solutions (ethanol, propanol, and benzene) were analyzed using modern nanostructure identification methods. The diameters of the synthesized multi-walled carbon nanotubes (MWNTs) ranged from 9 to 35 nm, single-walled carbon nanotubes (SWNTs) from 2 to 4 nm, and graphene flakes from 1 to 7 sheets, depending on the alcohol solution composition. Fullerene-like structures identified by HRTEM were obtained from a benzene mixture using electric arc vapor plasma synthesis. It is shown that the thermal steam plasma process with various alcohol solutions has great potential for the synthesis of nanotubes and graphene flakes due to the continuous and easy-to-implement method, cheap raw materials and adjustable carbon content due to the combination of different mixture compositions. Full article

Under severe ice and snow weather, ice-covered pantograph–catenary arcs affect the safe operation of high-speed trains. This study investigates the impact of ice-covered arc electrical characteristics, plasma parameters, and material ablation mechanisms. By constructing a comprehensive pantograph–catenary icing experimental platform, arc voltage, current signals, high-speed dynamic images, and emission spectra were synchronously collected under different icing thicknesses ranging from 0 to 15 mm. Research indicates that ice coverture causes frequent “extinction–reignition” phenomena during the arc initiation stage due to the latent heat absorbed by melting ice, significantly reducing the initial stability of arc combustion. Spectral analysis confirms that the arc excitation temperature and energy density are positively correlated with the concentration of hydrogen ions produced by water vapor ionization, reaching a peak under the 5 mm icing condition. Experimental results show that the average energy density of ice-covered arcs is approximately double that of the non-iced condition, causing the ablation pits on the carbon strip to exhibit characteristics of greater depth and wider copper deposition zones. This study reveals the unique mechanisms and damage characteristics of icing pantograph–catenary arcs, providing an important basis for the safe design and maintenance of pantograph–catenary systems in high-cold railway environments. Full article

Hydrogen plasma heating, a unique method for heating and reducing iron ore, is distinguished by its high heat, rapid reduction, and high efficiency, making it a promising technique in the metallurgy field. In this study, a non-transferred arc plasma heating system was used with Ar-H₂ as the working gas and acidic pellets as the raw material. The microstructures and elemental distributions of the slag and iron phases during the reduction process were examined using electron microscopy and energy-dispersive X-ray. The variation patterns of Fe-containing phases in the reduction products were found using X-ray diffraction and full-spectrum fitting refinement. The conversion rate of the oxidized pellets and the deoxidation conversion rate per area were estimated for various gas flow rates and reduction times. A reaction kinetics model was also used to study the reaction controlling step. The results showed that during the reduction process, with an H₂ flow rate of 4.5 L min⁻¹ and a 40 min reduction, the conversion(α) reached 99.89% and the purity of the reduced metallic iron reached 99.9%, achieving the industrial-grade 3N standard. Si and Al in the melt bath generated fayalite (Fe₂SiO₄) and hercynite (FeAl₂O₄) with Fe_xO. The deoxidation conversion rate per unit area was 1.11 g (cm² min)⁻¹. A three-dimensional diffusion-controlled model was used to describe the reduction process, and the mechanism function was 2/3(1 + α)^3/2[(1 + α)^1/3]⁻¹. The values of the reduction reaction rate constant (K) were 12.6 × 10⁻² s⁻¹ and 12.8 × 10⁻² s⁻¹ when the flow rates of H₂ gas were 3 and 4.5 L min⁻¹, respectively. The apparent activation energy was 21.9 kJ mol⁻¹. The empirical equation for the specific reduction rate was calculated as ln r = −2637.5/T − 0.407. Full article

To overcome the limitations of single-phase plasma-sprayed coatings, where ceramic coatings exhibit high hardness but poor toughness while metallic coatings possess good ductility but insufficient hardness, AT40/Al metal–ceramic composite coatings were prepared by atmospheric plasma spraying. In this study, Al₂O₃–40%TiO₂ (AT40) ceramic was used as the hard phase and aluminum as the ductile phase. The effects of Al content (10%, 20%, and 30%) and key spraying parameters, including arc power (36–40 kW), spraying distance (85–130 mm), and gun traverse speed (400–1200 mm s⁻¹), on the microstructure and mechanical properties of the coatings were systematically investigated. The coatings were characterized using SEM, XRD, and EDS, and grey relational analysis was employed to evaluate the influence of process parameters. The results show that the introduction of an appropriate amount of Al significantly improves coating densification. When the Al content is 10%, the coating porosity decreases to 3.2%, compared with 8.5% for the pure AT40 coating. The optimal spraying parameters were determined to be 38 kW arc power, 100 mm spraying distance, and 400 mm s⁻¹ traverse speed, under which the coating exhibits a microhardness of 519.68 HV and a 45.3% improvement in impact resistance compared with the pure AT40 coating. Phase analysis indicates that partial transformation of α-Al₂O₃ to γ-Al₂O₃ occurs during spraying, while interfacial reactions between Al and TiO₂ lead to the formation of Al₂TiO₅, enhancing the interfacial bonding strength. The improved performance of the composite coating is attributed to the combined effects of structural densification, interfacial strengthening, and the synergistic interaction between ceramic and metallic phases. Full article

This study investigates the feasibility of treating acidic gases produced in oilfields using a novel method that combines cavitation-jet reactor (CJR) technology with electric arc discharge (EAD). The integration of these two approaches enhances the ionization process by converting neutral gas molecules into chemically reactive ion-radical and radical fragments. These highly reactive species eventually recombine, creating new chemical compounds and simpler molecules from incoming acid gas and water vapor. Theoretical validation and experimental demonstration have revealed possible mechanisms and pathways of low-temperature plasma-chemical processes resulting from the synergistic effects of cavitating-jet flow and arc discharge on the molecular degradation of neutral gaseous molecules, such as hydrogen sulfide and carbon dioxide in water vapor, which lead to the generation of new compounds. Research indicates that the most effective method for processing associated petroleum gas (APG) involves minimizing the sequential nature of chemical reactions in low-temperature non-equilibrium plasma environments, thus eliminating the need for costly and complex catalysts. Additionally, studies have shown that the cavitation-jet flow of a gas–vapor–liquid mixture, when combined with an electric arc discharge in the truncated region of the low-temperature plasma of CJR, results in the synthesis of hydrogen, two forms of S₈ (S₈^I and S₈^II), crystalline carbon, and its organic derivatives containing oxygen and nitrogen, specifically methanol, ethanol, acetone, and acetonitrile. The data obtained suggest that the generation of low-temperature plasma in the cavitation-jet chamber, induced by an electric discharge, is essential for the production of reaction products, such as hydrogen, sulfur, and oxygen- and nitrogen-containing derivatives of organic carbon, when water vapor and acid gas molecules traverse the reactor. Full article

Wear of crushing and grinding equipment components causes frequent maintenance and downtime; therefore, effective repair hardfacing routes are required to extend service life. This study investigates plasma transferred arc (PTA) surfacing of 35L cast steel using a high-chromium Fe–Cr–C powder (PG-S27) and clarifies how the welding current (40–120 A) governs layer geometry, microstructure, phase constitution, hardness, and dry-sliding tribological behavior. All deposits exhibited a dendritic–eutectic structure; increasing current led to dendrite coarsening, wider interdendritic regions, and deeper penetration/dilution. X-ray diffraction indicated an α-Fe matrix with chromium carbide phases (Cr₇C₃/Cr₂₃C₆), while the carbide-related signal decreased with higher current, consistent with enhanced dilution. The coatings showed a strong hardening effect compared with the substrate (~190 HV), reaching ~625–650 HV at 40–80 A and decreasing to ~556–589 HV at 100–120 A. In dry ball-on-flat sliding, the steady-state friction coefficient was nearly unchanged (μ ≈ 0.50–0.55) across all regimes; however, wear resistance depended strongly on current: the lowest wear was achieved at low-to-moderate currents (40–80 A), whereas higher currents (100–120 A) resulted in substantially increased material loss, approaching the substrate level. These results identify 40–80 A as the most favorable current window for obtaining wear-resistant PTA layers from PG-S27 on 35L steel. Full article

Safe drinking water and microbial inactivation from surfaces and devices are among the World Health Organization’s priorities. Plasma-activated water (PAW) inactivates microorganisms mainly by producing radicals (hydroxyl radicals, superoxide, nitrogen oxide, etc.), which form secondary reactive species like nitrates, nitrites, hydrogen peroxide, etc., from the air–liquid interface, where the plasma interacts with the water. A plasma arc device for water treatment with enhanced arc length was constructed at the Andronikashvili Institute of Physics (TSU) and used in the study. PAW’s antibacterial efficacy has been evaluated against Gram-negative E. coli and remarkably stress-resistant Gram-positive B. pumilus. This study identifies reactive oxygen (hydrogen peroxide and superoxide anions) and nitrogen species (total nitrate and nitrite ions) in plasma-activated water, analyzing their potential impact on antioxidant enzyme activity and their relationships with bacterial cell viability. B. pumilus exhibits greater resistance to plasma-activated water as a disinfectant compared to E. coli. Catalase is more effective than superoxide dismutase in protecting cells from external oxidative stress, based on the two antioxidant enzymes studied. Full article

To enhance the quality and longevity of valve sealing surfaces, this study fabricated the Stellite 6/TiN composite coatings on F347 austenitic stainless steel. The process involved a plasma transferred arc (PTA) of Stellite 6 coating onto the substrate followed by physical vapor deposition (PVD) of a TiN coating onto the Stellite 6 layer. Mechanical testing revealed that the composite coatings achieved high hardness (~2110 HV), excellent adhesion (critical load Lc2 ~74 N), and superior wear resistance versus uncoated steel and single-layer Stellite 6. At 500 °C, the composite reduced wear volume by 97.2% compared to the uncoated substrate. Wear mechanisms for the Stellite 6 and composite coatings at high temperatures were elucidated, highlighting the role of Stellite 6/TiN composite coatings in enhancing tribological performance. Full article

This study reviews the application of wire arc additive manufacturing (WAAM) technology in maritime engineering and investigates an experimentally driven analytical approach for prediction of thermal distributions based on the Rosenthal solution. Two ER70S-6 low-carbon steel WAAM cylinders were fabricated using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes, with interlayer temperatures of 453 °C and 250 °C, respectively. Accurately measuring the temperature field to tailor the microstructure has long been a challenge. The results indicated a significant deviation between the analytical predictions and the experimental data. To address this discrepancy, a hybrid approach combining analytical and experimental results was implemented. Time intervals between layers, extracted from the experimental data, were incorporated into the Rosenthal equation to improve the accuracy of temperature field predictions. The microstructure at the bottom, middle, and top regions of the WAAM components was examined using optical microscopy. Tensile testing and Vickers microhardness measurements were conducted to evaluate mechanical properties. Scanning electron microscopy (SEM) was used to analyze fracture surfaces and identify fracture modes. The results were consistent with those reported for other ER70S-6 cylindrical WAAM components. This work highlights limitations of the Rosenthal solution and emphasizes the need for thermal models in WAAM applications. Full article