Search Results (2,146)

Silicon carbide (SiC) and SiC fiber-reinforced SiC matrix composites (SiC/SiC) are receiving renewed attention for use in next-generation fusion reactors due to their ability to withstand extreme conditions, including high temperatures, neutron irradiation, and plasma interactions. General Atomics Electromagnetic Systems (GA-EMS) has demonstrated significant progress in scaling up the fabrication of SiC/SiC, achieving high mechanical uniformity and meeting dimensional requirements in components up to 12 feet in length. Key developments are discussed including scale-up of the chemical vapor infiltration (CVI) process from lab-scale to full sized parts, high-dose (100 dpa) irradiation testing, nuclear-grade ceramic joining technologies, and production-focused quality control with the collective aim to establish SiC/SiC as a reliable solution for structural and functional components in fusion systems. Beyond manufacturing, the paper addresses supply chain barriers, particularly the limited availability and high cost of nuclear-grade SiC fiber. GA-EMS is developing a novel SiC fiber production method based on a thermochemical cure step that is anticipated to reduce costs compared to traditional approaches. Additionally, advancements in engineered SiC materials, such as SiC foams and tungsten-graded SiC composites, are discussed as promising solutions for specific fusion reactor components. Full article

The study investigates the catalytic activity of vanadium-containing catalysts in the selective oxidation of 4-methylpyridine (4-MP) in the gas phase. V-Cr, V-Ti, and V-Ti-Cr catalysts were synthesised and studied. The phase composition and structural features of the catalysts were determined by X-ray diffraction (XRD) and Raman spectroscopy, and their thermal stability was investigated using thermogravimetric analysis (TGA/DTA). Textural characteristics were evaluated by low-temperature nitrogen adsorption–desorption (BET, BJH), surface morphology was studied using scanning electron microscopy (SEM), and the distribution of elements was investigated using energy-dispersive X-ray spectroscopy (EDX). The chemical composition of the catalysts was determined using inductively coupled plasma atomic emission spectrometry (ICP-OES) and catalytic activity was evaluated in the selective gas-phase oxidation reaction of 4-methylpyridine in the temperature range 280–380 °C. It was found that an increase in temperature is accompanied by an increase in the conversion of 4-methylpyridine, but at the same time, deep oxidation reactions intensify. The best result is achieved on the V-Ti-Cr catalyst, for which the conversion of 4-MP reaches 86.88% and the selectivity is 73.06% at 320 °C. However, V-Ti provides moderate stable performance, while V-Cr demonstrates relatively low efficiency. Thus, it can be concluded that the nature of the temperature dependence of 4-methylpyridine conversion reflects the different nature of the active centres and their stability. Full article

Carbon fiber-reinforced polymer (CFRP) has been widely used in various fields due to its significant advantages. However, research on their pyrolysis and combustion behavior under fire conditions, which directly affects structural integrity and safety, remains insufficient. To challenge this issue, thermogravimetric analysis was employed to investigate the pyrolysis characteristics of the CFRP in both air and nitrogen atmospheres at heating rates of 20–40 °C/min with relevant pyrolysis kinetic parameters calculated using the Kissinger method. Fourier-transform infrared (FTIR) spectrometer was utilized to analyze pyrolytic gas species and concentrations at 40 °C/min in nitrogen atmosphere. Cone calorimeter tests at 50 kW/m² were conducted to obtain combustion characteristic parameters. Based on atomic conservation and oxygen-consumption principles, the equivalent molecular formula (CH_5.787O_0.541) of the epoxy resin pyrolysis gas and its combustion reaction equation were derived through reverse deduction. The heating, pyrolysis, and combustion processes of the CFRP (cone calorimetry specimen) were numerically simulated using Fire Dynamics Simulator (FDS). The predicted heat release rate, mass loss rate, and gas production rate showed good agreement with experimental results. Full article

Gas atomization is one method for producing fine metal powder. In close-coupled gas atomization, a high-speed gas jet is ejected near the molten metal, and the molten metal is further broken down in the shear layer at the outer edge of the jet, producing fine metal powder of several micrometers to several tens of micrometers. By the way, in close-coupled gas atomization, if the protrusion length of the molten metal nozzle is short, a backflow occurs that goes around the melt delivery nozzle tip and reaches the gas nozzle tip, and the small droplets of molten metal that are atomized at the exit of the melt delivery nozzle are carried by this backflow to the gas nozzle tip, causing it to erode. In this study, we experimentally clarified the existence of the backflow for the first time through measurements of velocity distribution, then the flow state of the gas flow inside the gas atomizer was visualized approximately using the atomized water flow, and the existence of a backflow was confirmed. It was shown that microdroplets of water are carried by the backflow and reach the gas nozzle tip. This was also clarified through numerical analysis results for the air flow. Furthermore, the protrusion length of the melt delivery nozzle at which backflow does not occur was determined, and this was verified in actual gas atomization experiments using molten copper. In addition, the length of the melt delivery nozzle at which backflow does not occur, i.e., the gas nozzle tip does not melt, was found. Furthermore, molten-copper experiments were conducted using this gas atomizer to evaluate its performance. Full article

Sustainable feedstock management remains a major challenge in laser beam powder bed fusion (PBF-LB), where conventional reuse strategies are typically limited to sieving and blending rather than full material regeneration. Ultrasonic atomization (UA) offers a fundamentally different powder production route based on capillary-wave instabilities induced at the surface of a molten metal by high-frequency vibrations. In contrast to turbulence-driven atomization, droplet formation in UA is primarily governed by ultrasonic frequency and intrinsic thermophysical properties of the melt, enabling quasi-deterministic particle formation with high sphericity and reduced satellite formation. In this study, ultrasonic atomization was investigated as a closed-loop route for converting PBF-LB-manufactured 316L stainless steel parts into reusable powder. Printed rods were remelted and atomized under controlled variation of electric current and vibration amplitude. The resulting powders were characterized in terms of morphology, internal microstructure, particle size distribution, chemical composition, and gas impurity content. UA produced highly spherical particles with reduced internal porosity and improved flowability compared to the initial gas-atomized powder, while preserving the principal alloying elements. An increase in oxygen content was observed after recycling, attributed to selective high-temperature oxidation under residual oxygen in nominally inert conditions. The results establish a mechanistic framework for transforming consolidated PBF-LB material into secondary feedstock and identify key parameters governing structural and compositional stability in closed-loop recycling. Full article

This study presents a unified first-principles investigation of CO₂, NO₂, SO₂, and H₂O adsorption on Al₂O₃ (001), TiO₂ (001), and SiO₂ (001) surfaces, establishing the first cross-material, chemically consistent benchmark for oxide–gas interactions. Calculated adsorption energies reveal strong chemisorption of SO₂ and NO₂ on Al₂O₃ and TiO₂, moderate H₂O binding—particularly on TiO₂ where hydroxylation is favored—and generally weak CO₂ interactions across all surfaces. Bader charge analysis provides atom-resolved insight into these trends, showing substantial electron transfer and pronounced oxygen-site polarization for strongly adsorbing gases, in contrast to the minimal charge redistribution characteristic of physisorbed CO₂. These charge-transfer signatures distinguish binding mechanisms, clarify the origins of material-specific selectivity, and link adsorption to expected variations in surface conductivity and sensor response. The combined energetic and electronic analysis also reveals competitive effects between humidity and CO₂ on surface hydroxylation and local electronic structure, a phenomenon critical for realistic sensing environments but previously unaddressed. Overall, this work delivers a rigorous comparative framework for understanding gas interactions with technologically relevant oxides and provides a solid foundation for future studies involving defects, dopants, surface reconstructions, and advanced functionalization strategies for environmental monitoring and energy-conversion devices. Full article

The separation of xenon (Xe) and krypton (Kr) is very important for industrial applications and environmental protection. However, the lack of permanent dipoles, low polarizabilities arising from their spherical nature, and similar kinetic diameters make their efficient separation by porous adsorbents exceptionally challenging. This study explored the effects of pore geometry and surface polarity of a series of aluminum-based metal–organic frameworks (CAU-10-H, MIL-160, KMF-1, CAU-23) on Xe/Kr separation performance using a heteroatom engineering strategy. These MOFs are composed of AlO₆ clusters and bent dicarboxylic acid linkers, enabling us to systematically investigate the effects of pore size and heteroatom types on Xe/Kr separation performance. Among them, MIL-160 has a polar linker based on furan, showing the best balance performance. At 298 K and 1.0 bar, the uptake of Xe is 4.12 mmol g⁻¹ and the IAST selectivity is 7.63 for a Xe/Kr (20/80) mixture. The practical performance was verified by dynamic breakthrough experiments, which yielded a long Xe breakthrough time of 42.9 min g⁻¹. Grand Canonical Monte Carlo (GCMC) simulations and first-principles density functional theory (DFT) calculations revealed that the enhanced performance originates from cooperative confinement and polarization effects, with the furanyl oxygen atoms providing optimal Xe-binding sites. This work clarifies the structure–property relationships governing Xe/Kr separation in aluminum-based MOFs (Al-MOFs), highlighting the potential of heteroatom engineering for designing efficient noble gas adsorbents. Full article

The food processing industry is seeking new technologies to enhance product safety, extend shelf life, and optimise food quality in response to growing consumer demand for high-quality products. Since the discovery of plasma technology, its potential applications in food processing have been numerous. For most of these applications, plasma characterisation is key to successfully scaling up from laboratory to industrial settings. A highly valuable tool for plasma characterisation is optical emission spectroscopy (OES), which serves as a non-invasive diagnostic method to monitor reactive species, specifically excited atoms and molecules (reactive oxygen and nitrogen species—RONS) that are critical for food treatment. The main role of OES in food control is to enable species identification and real-time process monitoring, providing feedback on electron temperature and density to prevent thermal damage to sensitive food products. It also facilitates optimisation by adjusting voltage and gas flow rates to maximise the production of antimicrobial species. These results ensure that processes are reliable and repeatable, supporting the transition from laboratory-scale to industrial applications. The paper provides an overview of the use of optical emission spectroscopy in various applications of plasma technology in food processing, including the determination of the elemental composition of raw materials and final products, detection of contaminants, quality control, determination of characteristic plasma parameters, and ensuring compliance with food safety regulations. Full article

Metal additive manufacturing relies on fine powders whose properties influence flow, spreading, and airborne release during processing, yet published data on powder characteristics, reuse effects, and emissions remain fragmented and difficult to compare. This study reviews quantitative measurements reported for metallic feedstocks used in laser powder bed fusion and directed energy deposition. A numerical evaluation model is developed to connect powder properties, process conditions, dispersion tendency, and material recovery. Particle size distribution values, density metrics, flow test results, reuse-related oxidation, and nanoparticle counts were compiled from the literature and normalized on a 0–1 scale. Four independent indices were defined: Material Fingerprint, process–powder interaction, airborne dispersion potential, and recovery. Adaptiveness refers to index sensitivity to changes in powder, reuse, and process conditions. The results indicate stable spreading for gas-atomized feedstocks, while wider particle size distributions and rougher surfaces increase cohesion and agglomeration, particularly under humid conditions and during reuse. Emission data indicate nanoparticle formation during processing, with recovery efficiency dependent on cyclone or high-efficiency particulate air filtration selection. The proposed model offers a screening approach for comparing powders and planning recovery strategies using data already available in the literature. Full article

The growing interest in functional beer production has led to the exploration of unconventional raw materials, such as hemp (Cannabis sativa L.), for brewing applications. This study aimed to evaluate the volatile organic compound (VOC) profile and the macro- and microelement composition of barley wort enriched with varying proportions (10% and 30%) of malted and unmalted hemp seeds, using solid-phase microextraction followed by gas chromatography–mass spectrometry (SPME–GC–MS) and atomic absorption spectrometry (AAS). A total of 64 VOCs were identified across four wort variants: control (barley malt only), 10% malted hemp, 30% malted hemp, and 30% unmalted hemp. The aroma profile was significantly influenced by compounds such as 2,3-butanediol, 1-hexanol, 3-methyl-1-butanol, 3-hydroxy-2-butanone, hexanoic acid, and 4-vinylguaiacol (p < 0.001). Principal component analysis (PCA) revealed clear separation between wort types based on the relative abundance of alcohols, acids, ketones, and phenols, indicating a progressive shift from sweet/malty toward acidic, green, and herbal aroma notes as hemp addition increased. Notably, unmalted hemp seeds resulted in a pronounced dominance of hexanoic acid, which may contribute to earthy and rancid sensory attributes. The evaluation of selected mineral elements showed that the key macroelements differentiating the worts were potassium, magnesium, phosphorus, and calcium, while among the microelements the distinguishing elements were manganese, iron, and sodium. These findings demonstrate the strong modulating effect of aromatic hemp-derived materials on the aroma composition and selected mineral content of brewing worts, supporting their targeted use in novel beer formulations. Full article

The significant disparity between the size and electronegativity of N and group-V (P, As, Sb) atoms in dilute III–V-Ns remains a cornerstone for developing the next-generation electronics. Variations in the structural, optical, and phonon properties of the quaternary GaAs_1−x−ySb_yN_x alloys are being used for improving the high-performance photovoltaic energy and optoelectronic technologies. Bandgap ${\mathrm{E}}_{\mathrm{g}}$ tunability has assisted efficient light emission/detection to cover the crucial optical fiber wavelengths for the low-cost integrated chips in data communications and sensing devices. The lattice dynamical properties of these materials are critical for assessing the reliability to evaluate the performance of long-wavelength lasers, photodetectors, and multi-junction solar cells. Our systematic Raman measurements on high-quality MBE grown $\mathrm{G}\mathrm{a}{\mathrm{A}\mathrm{s}}_{0.946}{\mathrm{S}\mathrm{b}}_{0.032}{\mathrm{N}}_{0.022}$/GaAs samples have detected ${\mathsf{\omega }}_{\mathrm{T}\mathrm{O}\left(\mathsf{\Gamma }\right)}^{\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}}$ and ${\mathsf{\omega }}_{\mathrm{T}\mathrm{O}\left(\mathsf{\Gamma }\right)}^{\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}}$ phonons along with a high frequency N_As local mode near ~476 cm⁻¹. Weak phonon structures on both sides of the broad 476 cm⁻¹ band are interpreted forming a complex N_As–Ga–Sb_As defect center. Using a realistic rigid-ion model in the Green’s function framework, the simulations of impurity modes for isolated and complex defects have provided corroboration to the experimental data. Full article

The time evolution of nanoscale structure formation on the surface of CdI₂ crystals grown both from the melt and from the gas phase is investigated. Atomic force microscopy was used to show that, already at the initial stages of exposure to air at room temperature, island-shaped nanostructures form, which subsequently aggregate into nanoclusters as the exposure time increases. Similar nanostructures, including nanopores and nanoclusters, are observed for CdI₂ crystals grown from the gas phase after prolonged exposure to air. Photoluminescence spectroscopy indicates that the formed nanoclusters are consistent with the presence of cadmium hydroxide (Cd(OH)₂) and cadmium oxide (CdO). The formation of nanostructures determines the time evolution of the low-temperature luminescence spectra of CdI₂ crystals. Additional bands with maxima at 1.87 eV and long-wavelength luminescence in the region with a maximum at 1.68 eV appear in the spectral structure. These results highlight the close relationship between surface structural evolution and the time-dependent optical properties of CdI₂. Full article

The first hydrogenation behavior of the gas atomized Ti_48.8Fe_46.0Mn_5.2 alloy was systemically investigated. The as-received powder showed no hydrogen absorption due to the long air exposure before the hydrogenation tests. To overcome this, 5 passes of cold rolling were employed as an activation strategy. Cold rolling introduced cracks and defects that facilitated hydrogen diffusion, enabling the alloy to successfully absorb hydrogen. The influences of temperature, constant driving force, and hydrogen pressure on the first hydrogenation were evaluated. The results indicated that the first hydrogenation follows an Arrhenius behavior ($\mathrm{k}=\mathrm{A}{\mathrm{e}}^{-{\displaystyle \frac{{\mathrm{E}}_{\mathrm{a}}}{\mathrm{R}\mathrm{T}}}}$), and average activation energy was calculated as 71 kJ/mol H₂. The pre-exponential factor (A) was found to be pressure-dependent, following the equation A = A₀ (P/P₀)^1.8, where A₀ = 2.6 × 10⁶ s⁻¹. Full article

Green cosmetics are primarily based on plant-derived ingredients and use sustainable biotechnological tools for their preparation. The present research aimed to investigate the Usnea barbata (U. barbata) extract in Jojoba oil (JO) enriched with 5% Peppermint oil (PEO) and 10% Vitamin E, as a potential natural product for skin applications. The U. barbata oil extract (UBPJO) was obtained through cold maceration. Phytochemical screening was performed using Gas Chromatography/Mass Spectrometry (GC-MS), Folin–Ciocalteu method, and Graphite-Furnace Atomic Absorption Spectrophotometry (GFAAS). Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM) were used to evaluate the physicochemical properties. Then, rheological characteristics and oxidation stability (measured as the time to reach the oxidation starting point, induction period (IP)) of both oil samples (UBPJO and oil mixture alone (PJO) were investigated. Total phenolic content (TPC) in UBPJO was 2.5 times higher than in PJO (p < 0.05), while heavy metal levels (As and Pb) were slightly higher (p > 0.05). UBPJO has higher shear stress, viscosity, and spreadability than PJO, but the differences are not significant (p > 0.05). Finally, IP measurements indicated appreciable oxidative stability (UBPJO vs. PJO: 153.02 h vs. 137.35 h, p > 0.05). The phytochemical composition and physicochemical properties support the inclusion of UBPJO in various skincare formulations. Full article

N₂O emissions exacerbate the greenhouse effect, urgently demanding advances in abatement technologies. Catalytic decomposition of N₂O over cobalt-based oxides with alkali metal promoters remains challenging because these catalysts are used in pelletized form, limiting their activity to a narrow outer-shell region due to internal diffusion limitations. However, research efforts continue to focus on enhancing Co–alkali metal contact on unsupported powder samples under inert conditions, even though, under industrial conditions, catalysts are exposed to inhibitory components of waste gases and N₂O, and the powder form is unsuitable for practical application. This study aims at testing N₂O decomposition over catalysts with a Co₃O₄-Cs active phase supported on a ceramic foam. For this purpose, we characterized these catalysts by H₂ temperature-programmed reduction, H₂O and NO temperature-programmed desorption, atomic absorption spectroscopy, and X-ray diffraction and assessed their catalytic performance under an inert-gas atmosphere and with O₂, water vapor, and NO to simulate industrial conditions. Using a pseudo-homogeneous, one-dimensional model of an ideal plug flow reactor in an isothermal regime, the simulation calculations for a full-scale catalytic reactor for N₂O abatement in waste gas from HNO₃ production were performed. The Cs₂CO₃ precursor significantly enhanced catalyst reducibility and electron transferability, increasing N₂O decomposition efficiency in inert gas, but its high hygroscopicity decreased resistance to water vapor and NO, overriding its advantages under industrial conditions. Conversely, glycerol-assisted impregnation enhanced catalyst performance regardless of Cs precursor. These foam-supported catalysts offered several other advantages, including lower pressure drop and lower active phase loading with matching catalytic activity. Based on our findings, depositing Cs₂CO₃ on ceramic foam through glycerol-assisted impregnation may facilitate catalytic N₂O decomposition at the industrial level and, therefore, promote environmental sustainability by reducing N₂O emissions. Full article