Search Results (169)

When processing widely used materials in welded structures such as steels, a surface operation such as plasma cutting applied in the automated Computer Numerical Control (CNC) version can provide technical and economic benefits to the cut components, but the impact on health and environment must be addressed accordingly. In this paper, a plate with a base material made of S355J2 + AR structural steel is cut in 10 pieces with plasma in a water-bed designed and manufactured by the authors in order to mitigate such risks. The surfaces cut in the water-bed are compared to surfaces cut in open air by macroscopic analyses of the edge cut, by microscopic analyses of the cut parts—base material, heat-affected zone, and cut area—and by hardness determinations. The results reveal improvements as a result of plasma cutting in the water-bed: slag reduction, preservation of granulation, transformations in the austenitic temperature zone, and hardness in the heat-affected zone. Compared to a classical cutting procedure such as oxygen flame cutting, the proposed procedure offers a clean alternative and also requires low maintenance. Full article

Titanium (Ti) alloys, renowned for their exceptional physicochemical properties and high biocompatibility, are widely utilized in orthopedic and dental implants; however, their lack of intrinsic antimicrobial activity significantly increases the risk of implant-associated infections, often leading to severe complications and implant failure. Developing antimicrobial coatings on Ti implants is therefore a promising strategy. In this study, tannic acid (TA) coatings were deposited by immersing Ti alloy surfaces—beforehand activated by low-temperature oxygen plasma—in TA solutions at 2, 5, and 8 wt%. Coatings were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurements, and Folin–Ciocalteu release assays, and their cytocompatibility and antimicrobial performance were assessed in vitro. Surface characterization confirmed the formation of uniform TA layers, and WCA measurements indicated enhanced hydrophilicity relative to unmodified Ti (82.0° ± 3.6°), with values decreasing as TA concentration increased (from 35.2° ± 3.2° for 2% TA to 26.6° ± 2.8° for 8% TA). TA release profiles exhibited an initial burst followed by sustained diffusion, with 5% and 8% coatings releasing significantly more TA than 2% coatings. Coatings containing ≥ 5% TA demonstrated bactericidal activity—achieving > 2-log₁₀ reductions—against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, and also showed inhibitory effects against Candida albicans. Importantly, all coatings remained cytocompatible with NIH/3T3 fibroblasts, and the released tannic acid hydrolysis products (particularly gallic acid) enhanced their proliferation. These findings indicate that plasma-activated titanium surfaces coated with ≥5 wt% tannic acid impart broad-spectrum antimicrobial efficacy and hold potential to reduce implant-associated infections and improve long-term outcomes in orthopedic and dental applications. Full article

TbCu₇-type Sm-based compounds can be produced in bulk and potentially surpass Nd₂Fe₁₄B as permanent magnets. However, as the processes to prepare anisotropic magnetic particles are limited, the full potential of TbCu₇-type Sm-based compounds cannot be exploited. In this study, metastable TbCu₇-type phases of anisotropic Sm–Fe–N ultrafine particles were prepared using the low-oxygen induction thermal plasma (LO-ITP) process. X-ray diffraction analysis revealed that the obtained TbCu₇-type Sm–Fe alloy nanoparticles exhibited a c/a value of 0.8419, with an Fe/Sm atomic ratio of ~8.5. After nitrogenation, the obtained Sm–Fe–N nanoparticles were aligned under an external magnetic field, indicating that each alloy particle exhibited anisotropic magnetic properties. A substantially high degree of alignment of 91 ± 2% was achieved, quantitatively estimated via pole figure measurements. Numerical analysis following Sm–Fe nanoparticle formation showed that, compared with Fe condensation, Sm condensation persisted even at low temperatures, because of a significant difference in vapor pressure between Sm and Fe. Though this led to a relatively large compositional distribution of Sm within particles with a Sm concentration of 9–12 at%, the preparation of single-phase TbCu₇-type Sm–Fe–N particles could be facilitated by optimizing several parameters during the LO-ITP process. Full article

Polyaryletherketone (PAEK) polymers inherently exhibit low surface activity, leading to poor adhesive bonding performance when using epoxy-based adhesives. In this study, low-temperature plasma surface modification was conducted on carbon fiber-reinforced polyetherketone ketone (CF/PEKK) composites to investigate the influence of plasma treatment parameters on their lap shear strength. Surface characterization was systematically performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle analysis to evaluate morphological, chemical, and wettability changes induced via plasma treatment. The results demonstrated a significant enhancement in lap shear strength after plasma treatment. Optimal bonding performance was achieved at a treatment speed of 10 mm/s and a nozzle-to-substrate distance of 5 mm, yielding a maximum shear strength of 28.28 MPa, a 238% improvement compared to the untreated control. Notably, the failure mode transitioned from interfacial fracture in the untreated sample to a mixed-mode failure dominated by cohesive failure of the adhesive and substrate. Plasma treatment substantially reduced the contact angle of CF/PEKK, indicating improved surface wettability. SEM micrographs revealed an increased micro-porous texture on the treated surface, which enhanced mechanical interlocking between the composite and adhesive. XPS analysis confirmed compositional alterations, specifically elevated oxygen-containing functional groups on the plasma-treated surface. These modifications facilitated stronger chemical bonding between CF/PEKK and the epoxy resin, thereby validating the efficacy of plasma treatment in optimizing surface chemical activity and adhesion performance. Full article

Aflatoxins are toxic organic substances that are synthesized on the surfaces of seeds, nuts, and similar products by some fungi under elevated humidity. They decompose at temperatures well above 130 °C, so standard heating or autoclaving is an obsolete technique for the degradation of toxins on surfaces without significant modification of the treated material. Non-equilibrium plasma was used to degrade aflatoxins at low temperatures and determine the efficiency of O atoms. A commercial mixture of aflatoxins was deposited on smooth substrates, and the solvent was evaporated so that about a 3 nm thick film of dry toxins remained on the substrates. The samples were exposed to low-pressure oxygen plasma sustained by an inductively coupled radiofrequency (RF) discharge in either the E or H mode. The gas pressure was 20 Pa, the forward RF power was between 50 and 700 W, and the O-atom flux was between 1.2 × 10²³ and 1.5 × 10²⁴ m⁻² s⁻¹. Plasma treatment caused the rapid degradation of aflatoxins, whose concentration was deduced from the fluorescence signal at 455 nm upon excitation with a monochromatic source at 365 nm. The degradation was faster at higher discharge powers, but the degradation curves fitted well when plotted against the dose of O atoms. The experiments showed that the aflatoxin concentration dropped below the detection limit of the fluorescence probe after receiving the O-atom dose of just above 10²⁵ m⁻². This dose was achieved within 10 s of treatment in plasma in the H mode, and approximately a minute when plasma was in the E mode. The method provides a low-temperature solution for the efficient detoxification of agricultural products. Full article

Flower senescence during transport is a major concern for exporters, as physiological disorders reduce quality and price. Extending vase life is crucial, and while 1-MCP is widely used, it requires low temperatures and is less effective in disease control. Cold plasma generated by dielectric barrier discharge produces reactive oxygen and nitrogen species (RONS), offering an alternative method for preserving cut flowers. This study compared the effectiveness of cold plasma and 1-MCP treatments on the vase life of Vanda ‘Pachara Blue’ orchids. Flowers were treated with T1 (control at 25 °C), T2 (1-MCP), and T3 (cold plasma). Both 1-MCP and cold plasma significantly reduced ethylene production (26.15 and 25.20 µL C₂H₄/kg/hr, respectively) and respiration rate (63.92 and 57.44 mg CO₂/kg/hr, respectively) compared to the control (40.93 µL C₂H₄/kg/hr and 118.21 mg CO₂/kg/hr). Vase life was extended to 19.33 days in both treatments, an 87.12% increase over the control (10.33 days). Additionally, cold plasma slightly improved water uptake and reduced petal discoloration. These findings indicate that cold plasma is a promising alternative to 1-MCP, offering effective flower preservation without the need for low-temperature conditions and potential additional benefits in floral quality. Full article

Previous studies have demonstrated that underwater low-temperature plasma is effective for synthesizing nanomaterials by generating plasma discharges between metal electrodes submerged in water. This study extends this approach to the one-step synthesis of MXenes containing titanium, molybdenum, and titanium–molybdenum composites through pulsed discharges in carbon tetrachloride, an oxygen-free, non-flammable solvent characterized by a high boiling point and low permittivity. By employing titanium and molybdenum electrodes in various configurations, three MXene samples were synthesized: Ti₂CT_X, Mo₂CT_X, and Mo₂TiC₂T_X. Characterization techniques, including UV-Vis spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, confirmed the successful synthesis of high-purity MXenes with distinct structural and optical properties. Notably, the bandgap values of the synthesized MXenes were determined as 1.71 eV for Ti₂CT_X, 1.42 eV for Mo₂TiC₂T_X, and 1.07 eV for Mo₂CT_X. The photocatalytic performance of the synthesized MXenes was evaluated, showing a removal efficiency of 65% to 98% for dye mixtures, with methylene blue showing the highest degradation rate. This plasma-assisted method offers a scalable, precursor-free route for the synthesis of MXenes with potential applications in energy storage, environmental remediation, and optoelectronics due to their tunable bandgaps and high catalytic activity. Full article

The selection of a suitable plasma-facing material (PFM) that must protect the divertor, cooling systems, and structural components is an important challenge in the design of advanced fusion reactors and requires careful consideration. Material degradation due to melting and evaporation may lead to plasma contamination, which must be strictly avoided. Among the candidate materials, tungsten (W) is the most promising because of its thermo-mechanical and physical properties, which allow it to endure repeated exposure to extremely harsh conditions within the reactor. The plasma spraying (PS) technique is gaining increasing interest for the deposition of tungsten (W) coatings to protect heat sink materials, due to its relatively low cost, high deposition rates, and capability to coat complex-shaped surfaces and fix damaged coatings in situ. This review aims to provide a systematic assessment of tungsten (W) coatings produced by PS techniques, evaluating their suitability as PFMs. It discusses W-based materials, plasma spraying technologies, the role of the interface in joining W coating and metallic substrates such as copper alloys and steels, and the main issues related to coating surface erosion under steady-state and transient heat loads associated with advanced fusion reactor operation modes and off-normal events. Quantitative data available in the literature, such as porosity, oxygen content, thermal conductivity of the coatings, residual stresses accumulated in the coating–substrate interface, surface temperature, and material loss following heat load events, were summarized and compared to bulk W ones. The results demonstrate that, following optimization of the fabrication process, PS-W coatings exhibit excellent performance. In addition, previously mentioned advantages of PS technology make PS-W coatings an attractive alternative for PFM fabrication. Full article

Low temperature plasmas (LTPs) generated at atmospheric pressure and room temperature have gained increasing attention in biomedical research due to their ability to control cellular behavior through the production of reactive oxygen and nitrogen species (RONS), electric fields, and UV radiation. Among several LTP configurations, dielectric barrier discharge (DBD) plasma has been extensively studied for its ability to stimulate controlled biological effects while maintaining low gas temperature, making it suitable for cell-based applications. This study designed a novel spiral-wound DBD plasma device to investigate the voltage-dependent effects of plasma discharge on DBC1.2 epithelial cells. Plasma was applied at 2 kV_p-p, 3 kV_p-p, and 4 kV_p-p to evaluate its effect on cellular permeability, mitochondrial activity, viability, and apoptosis. FITC-dextran-70 (FD-70, MW: 70 kDa) was used as a model permeation marker to assess cellular uptake. The results showed a voltage-dependent increase in FD-70 uptake, suggesting improved plasma-assisted drug delivery. The cell mitochondrial activity, evaluated with a MT-1 MitoMP detection kit, revealed that plasma exposure at 2 kV_p-p and 3 kV_p-p slightly enhanced mitochondrial membrane potential (MMP), signifying increased metabolic and mitochondrial activity, whereas exposure at 4 kV_p-p led to a reduction in MMP, suggesting oxidative stress and early apoptosis. Early and late apoptosis was further assessed using FITC Annexin-V and propidium iodide (PI). The results showed enhanced cell viability and a reduced apoptotic cell at 2 kV_p-p and 3 kV_p-p plasma exposure when compared to the control. However, at 4 kV, there was a decline in cell viability and an increase in apoptosis, suggesting a shift towards plasma-induced cytotoxicity. This study established a safe plasma exposure threshold for DBC1.2 cells and explored the potential use of a spiral-wound DBD plasma device for biomedical applications, particularly in drug delivery and cell modulation. Full article

A growing interest in novel noble metal-free electrocatalysts is fuelled by the pressing need to overcome the drastic demand for sustainable energy sources. To this end, the oxygen evolution reaction (OER) utilising transition metal oxide–carbon composites in alkaline media is considered a robust technology. In many such systems, carbon is used as a conductive additive or support, and the interactions between carbon support materials and the active phase affect the efficiency of the electrocatalyst. Cobalt forms some of the most active and stable electrocatalysts for OER. In carbon-supported systems, the dispersion of the cobalt phase on the carbon surface is a key factor in influencing the catalyst activity in water-splitting reactions. In this study, a low-temperature plasma treatment is used to boost the efficiency of the cobalt active phase by functionalising the carbon support with various oxygen groups. We used a simple deposition–precipitation method to obtain cobalt hydroxide active phase over graphene nanoparticles. The activation of graphene nanoparticles with oxygen plasma allowed us to obtain a catalyst that showed only 317 mV@10 mA·cm⁻². More importantly, in the series of plasma-activated samples, the OER activity was very high in a range of cobalt phase loadings, yielding a material with 2.4 wt.% of cobalt and an overpotential of only 327 mV@10 mA·cm⁻². The results indicate that plasma activation of GNP support maximises the usage of the transition metal active phase, which allows for an improvement in area-normalised and a dramatic improvement in the mass-normalised OER electrocatalytic activity. Full article

The global reliance on fossil fuels, particularly natural gas, underscores the urgency of developing sustainable methods for methane (CH₄) and carbon dioxide (CO₂) conversion. Methane, which constitutes 95% of natural gas, is a critical feedstock and fuel source. However, its high bond dissociation energy and volatility pose challenges for large-scale utilization and transport. Current research emphasizes the catalytic and plasma-assisted conversion of CH₄ and CO₂ into value-added products such as methanol, higher hydrocarbons, and organic oxygenates. Advancements in these technologies aim to overcome obstacles such as high operating temperatures, coking, and low product selectivity while addressing methane’s environmental impact, as leakage during extraction and distribution significantly contributes to global warming. Plasma-assisted conversion has emerged as a promising approach, leveraging electron impact processes to generate reactive species that facilitate CH₄ and CO₂ transformation at near-room temperatures. The integration of catalysts within plasma environments enhances reaction pathways, product yields, and selectivity by modifying plasma properties and surface interactions. This review comprehensively discusses the various methods investigated for CH₄ conversion and energy efficiency. We attempt to highlight the recent progress in plasma-assisted catalytic processes for CH₄ and CO₂ valorization, with a focus on the mechanisms of product formation, catalyst modifications, and their impact on plasma discharge characteristics. The insights gained could pave the way for scalable, energy-efficient solutions to produce sustainable fuels and chemicals, thereby contributing to global efforts in carbon cycle fixation and climate change mitigation. Full article

The Yidun island arc was formed in response to the Late Triassic westward subduction of the Ganzi–Litang oceanic plate, a branch of the Paleo-Tethys Ocean. The Zhongdian arc, located in the south of the Yidun island arc, has relatively large number of porphyry (skarn) type Cu–Mo ± Au polymetallic deposits, the largest of which is the Pulang Cu (–Mo–Au) deposit with proven Cu reserves of 5.11 Mt, Au reserves of 113 t, and 0.17 Mt of molybdenum. However, the relationship between mineralization and the potassic alteration zone, phyllic zone, and propylitic zone of the Pulang porphyry deposit is still controversial and needs further study. Titanite (CaTiSiO₅) is a common accessory mineral in acidic, intermediate, and alkaline igneous rocks. It is widely developed in various types of metamorphic rocks, hydrothermally altered rocks, and a few sedimentary rocks. It is a dominant Mo-bearing phase in igneous rocks and contains abundant rare earth elements and high-field-strength elements. As an effective geochronometer, thermobarometer, oxybarometer, and metallogenic potential indicator mineral, titanite is ideal to reveal the magmatic–hydrothermal evolution and the mechanism of metal enrichment and precipitation. In this paper, major and trace element contents of the titanite grains from different alteration zones were obtained using electron probe microanalysis (EPMA) and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to define the changes in physicochemical conditions and the behavior of these elements during the process of hydrothermal alteration at Pulang. Titanite in the potassic alteration zone is usually shaped like an envelope. It occurs discretely or is enclosed by feldspar, with lower contents of CaO, Al, Sr, Zr and Hf; a low Nb/Ta ratio; high ∑REE + Y, U, Th, Ta, Nb, and Ga content; and high FeO/Al₂O₃ and LREE/HREE ratios. This is consistent with the characteristics of magmatic titanite from fresh quartz monzonite porphyry in Pulang and other porphyry Cu deposits. Titanite in the potassium silicate alteration zone has more negative Eu anomaly and a higher U content and Th/U ratio, indicating that the oxygen fugacity decreased during the transformation to phyllic alteration and propylitic alteration in Pulang. High oxygen fugacity is favorable for the enrichment of copper, gold, and other metallogenic elements. Therefore, the enrichment of copper is more closely related to the potassium silicate alteration. The molybdenum content of titanite in the potassium silicate alteration zone is 10²–10⁴ times that of the phyllic alteration zone and propylitic alteration zone, while the copper content is indistinctive, indicating that molybdenum was dissolved into the fluid or deposited in the form of sulfide before the medium- to low-temperature hydrothermal alteration, which may lead to the further separation and deposition of copper and molybdenum. Full article

Sustainable agriculture faces major issues with resource efficiency, nutrient distribution, and plant health. Traditional soil-based and soilless farming systems encounter issues including excessive water use, insufficient nutrient uptake, nitrogen deficiency, and restricted plant development. According to the previous literature, aeroponic systems accelerate plant growth rates, improve root oxygenation, and significantly enhance water use efficiency, particularly when paired with both low- and high-pressure misting systems. However, despite these advantages, they also present certain challenges. A major drawback is the inefficiency of nitrogen fixation, resulting in insufficient nutrient availability and heightened plant stress from uncontrolled misting, which ultimately reduces yield. Many studies have investigated plasma uses in both soil-based and soilless plant cultures; nevertheless, however, its function in aeroponics remains unexplored. Therefore, the present work aims to thoroughly investigate and review the integration of plasma-activated water (PAW) and plasma-activated mist (PAM) in aeroponics systems to solve important problems. A review of the current literature discloses that PAW and PAM expand nitrogen fixation, promote nutrient efficiency, and modulate microbial populations, resulting in elevated crop yields and enhanced plant health, akin to soil-based and other soilless systems. Reactive oxygen and nitrogen species (RONS) produced by plasma treatments improve nutrient bioavailability, root development, and microbial equilibrium, alleviating critical challenges in aeroponics, especially within fine-mist settings. This review further examines artificial intelligence (AI) and the Internet of Things (IoT) in aeroponics. Models driven by AI enable the accurate regulation of fertilizer concentrations, misting cycles, temperature, and humidity, as well as real-time monitoring and predictive analytics. IoT-enabled smart farming systems employ sensors for continuous nutrient monitoring and gas detection (e.g., NO₂, O₃, NH₃), providing automated modifications to enhance aeroponic efficiency. Based on a brief review of the current literature, this study concludes that the future integration of plasma technology with AI and IoT may address the limitations of aeroponics. The integration of plasma technology with intelligent misting and data-driven control systems can enhance aeroponic systems for sustainable and efficient agricultural production. This research supports the existing body of research that advocates for plasma-based innovations and intelligent agricultural solutions in precision farming. Full article

Oxidative stress is universal to all cell types, including cancer. It is elicited by a surplus of reactive oxygen species (ROS) or a reduced cellular ability to defend against those. At low levels (oxidative eustress), this induces altered cellular signaling, while at higher levels (oxidative distress), cellular toxicity and non-specific redox signaling become apparent. While oxidation-induced cell death is a hallmark of many cancer therapies, including ROS-producing radiotherapy, some chemotherapies and targeted therapies, photodynamic therapy, and recently emerging physical modalities such as medical gas plasma (a multi-ROS generating technology), less is known about the transcriptional profiles predisposing cancer cells to oxidative demise. In particular, which genes are associated with resistance or sensitivity to ROS overload and subsequent toxicity has not been systematically investigated. Moreover, it is unclear if there are differences between oxidant types, such as hydrogen peroxide and hypochlorous acid. To this end, we here employed 35 cell lines of various origins (e.g., adenocarcinoma, melanoma, leukemia, squamous cell carcinoma, and neuroblastoma). We first performed in-house transcriptomic analysis to assess baseline transcriptional profiles. Second, all cell lines were exposed to four different ROS concentrations of either hydrogen peroxide, hypochlorous, or gas plasma exposure. Third, correlation analysis was performed to identify genes associated with (i) oxidative stress sensitivity, (ii) oxidative stress resistance, and (iii) similarities and/or differences between the different oxidative stress inducers. Intriguingly, distinct gene sets were found for all treatments, and there was a striking difference between hydrogen peroxide and hypochlorous acid, suggesting different modes of action of both oxidants. Full article

As reported during the last five years, SnSe is one of the leading thermoelectric (TE) materials with a very low lattice thermal conductivity. However, its elements are not as heavy as those of classical thermoelectric materials like PbTe or Bi₂Te₃. Its outstanding TE properties were revealed after repeated purification steps to minimize the amount of oxygen contamination, followed by spark plasma sintering. Recently, we showed that hot-pressing—once optimized—can yield comparable or even better TE performance using the examples of Na- and Cu- as well as Na- and Ag-co-doped SnSe. However, long-term stability remains a challenge during cycling between low and high temperatures. Here, we investigated whether the cooling procedure has a significant impact on the thermoelectric properties of SnSe. We compared cooling of the melt with a 1:1 ratio of Sn:Se from 1273 K down to room temperature in air with quenching in water. As typical for undoped SnSe, both materials were extrinsic p-type semiconductors due to Sn defects. The air-quenched sample exhibited higher thermal conductivity, lower electrical conductivity, and higher Seebeck coefficient, all consistent with a smaller number of defects and thus a smaller number of charge carriers due to the slower cooling procedure. This resulted in a comparatively low peak figure-of-merit value zT of 0.61 at 823 K for the air-quenched sample, compared to the substantially higher peak zT of 1.58 at 813 K for the water-quenched sample. Full article