Search Results (10,354)

The methanol oxidation reaction was investigated on Co- and/or Ag-based γ-Al₂O₃ catalysts, which were prepared by different methods (WI: wet impregnation and SI: spray impregnation) and further doped with noble metals (Pd, Pt). During the present study, three different reaction pathways were revealed. The complete oxidation of methanol to CO₂ and H₂O was achieved on Pd-doped catalysts prepared by the spray impregnation method (Pd-Co/Al-SI and Pd-Ag/Al-SI), while partial oxidation to intermediates such as formaldehyde was observed for Ag/alumina catalysts. The dehydration reaction of methanol to dimethyl ether was carried out on Co/alumina, Ag-Co/alumina, and Pt-Co/alumina catalysts. The improved reducibility of the 5Co/Al-SI catalyst with the incorporation of Pd, combined with the easier surface oxygen desorption, resulted in higher catalytic activity compared to the Pt-doped catalyst. On the other hand, the incorporation of Pd into Ag/Al-SI enhanced the well-dispersed Ag₂O species, mainly affecting the structural properties of the catalyst, thus resulting in partial oxidation of methanol. The 0.5 wt.% Pd-5 wt.% Co/γ-Al₂O₃ catalyst, prepared by the spray impregnation method, exhibited the highest methanol oxidation efficiency (T₅₀: 43 °C) and was further evaluated in the presence of H₂O and CO in the feed for several hours on stream and at reaction temperature of 230 °C. The presence of impurities initially reduced the catalyst’s activity from 100% methanol conversion (in the absence of H₂O and CO in the feed) to 80%; however, over time complete methanol oxidation was regained (achieving again 100% methanol conversion after 12 h on stream). Characterization of the used catalyst (after the stability experiment) revealed that in addition to the Co₃O₄ phase, initially formed in the fresh, as-prepared catalyst, some Co₃O₄ species were reduced to CoO under the reaction conditions, suggesting that the active phase of the 0.5Pd-5Co/Al-SI catalyst for the methanol oxidation reaction in the presence of the impurities (such as H₂O and CO) is probably a mixture of Co₃O₄ and CoO phases. Full article

Foodborne chemical exposure is a significant public health concern. Various chemical agents found in foods, including pesticide residues, heavy metals, natural toxins, compounds formed during food processing, and food additives, may result in carcinogenic or noncarcinogenic health effects in the long term. Along with discussing the main sources of dietary chemical exposure and its health impacts, this review article also covers the theoretical foundations and four main steps of chemical risk assessment. Furthermore, risk assessment approaches are investigated in the light of international organizations and guidelines, and the current debates and challenges within the field are underscored. Lastly, suggestions for safer food supply and potential future developments are presented. This comprehensive review may provide a current literature-based viewpoint on comprehending and addressing dietary chemical-associated public health issues. Full article

This article presents the results of experimental investigations conducted to explain the causes of premature failure of two leaves of a semi-elliptical leaf spring mounted in a four-axle heavy-duty truck. The primary intended use of the vehicle was the continuous transport of cargo on unpaved roads with large, non-uniform irregularities. The vehicle equipped with the springs in question was loaded with a constant cargo placed in a rigid container. The Gross Vehicle Mass (GVM) was 32,000 kg (8000 kg/axle). During operation, it mostly traveled on rough terrain and off-road, at an average speed not exceeding 30 km/h. The semi-elliptical leaf springs used in the vehicle were supplied by a domestic manufacturer and produced according to a standard procedure that has been used for years. The experimental research included strain measurements of the springs during normal vehicle operation. In parallel, metallographic examinations of the fractured surfaces of the leaves were performed. The stress intensity (or stress state) of the springs in the vicinity of the resulting crack was also checked using the Finite Element Method (FEM). Subsequently, the fatigue life of the springs was estimated based on fatigue data available in the literature and the results of the conducted research. Full article

Soil co-contamination with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) represents a widespread and challenging environmental issue that is difficult to address using conventional remediation methods. This review systematically examines the molecular mechanisms by which plant root exudates mediate the remediation of co-contaminated soils through synergistic interactions with rhizosphere microorganisms. We detail how plants dynamically adjust the composition and secretion of root exudates—such as organic acids, amino acids, sugars, and secondary metabolites—in response to combined HM-PAH stress. These exudates play multifaceted roles in remediation, including chelating HMs, enhancing PAH solubility and bioavailability, and acting as chemoattractants and metabolic substrates for rhizosphere microbes. In return, the recruited microbial communities contribute to pollutant detoxification through various mechanisms, such as biosurfactant production, enzymatic degradation, and improved plant nutrient acquisition. This reciprocal interaction forms a synergistic plant-microbe feedback loop that effectively mitigates combined contamination stress. By integrating evidence from diverse plant–soil systems, this review provides a comprehensive mechanistic framework for understanding root exudate-microbe interactions, offering critical insights for developing enhanced phytoremediation strategies to address complex environmental pollution. Full article

Additive manufacturing (AM) offers opportunities to advance the design and function of ceramic tooling in high temperature actinide pyrochemistry. In technical ceramics such as alumina, conventional forming techniques often restrict design flexibility and can limit experimental progress. In this study, we investigate the use of vat photopolymerization (VP) with commercial resins to fabricate large-scale alumina crucibles, reaching dimensions up to 125 mm, which is significantly larger than typically reported for dense VP ceramics. Notably, these additively manufactured components are produced using consumer-grade hardware, which limits process control, but offers significant upside in scalability and accessibility. Using microscopy and X-ray computed tomography, the VP alumina parts have high bulk densities above 95%, but also the prevalence of AM-induced artifacts and surface defects. Mechanical testing showed these defects to significantly reduce flexural strength and compromise part reliability. Electrorefining trials under sustained exposure to molten salts and metals reveal mixed results, with the AM material exhibiting high chemical compatibility, but mechanical failures due to the reduced strength were prevalent. Our findings illustrate both the promise and current limitations of AM ceramics for actinide chemistry, and point toward future improvements in process optimization, design strategies, and part screening to enhance performance and reliability. Full article

Heavy metals (HMs) were originally formed in the universe long before human evolution and are now ubiquitous in the environment, where some HMs are good as essential elements for human health while others are not. The purpose of this analytical review is to provide an updated clinical overview on health risks attributable to drinking water containing specific HMs and to discuss new aspects of molecular steps leading to disrupted diseases. This approach was favored because the study cohorts were homogeneous, since exposed individuals lived in households where all members had access to the same drinking water of constant quality. Among the HMs under consideration, aluminum, arsenic, cadmium, chromium, copper, iron, lead, manganese, and mercury were detected in drinking water and represented a health risk if levels were above thresholds recommended by national and international regulatory authorities. For example, (1) aluminum increased the risk of dementia and Alzheimer’s disease; (2) arsenic was associated with the development of bladder cancer; (3) cadmium increased the no-carcinogenic, as well as the carcinogenic, health risk; (4) chromium was considered as a risk factor for liver and kidney injury, as well cancer development; (5) copper contributed to cognitive impairment in the aging population and Alzheimer’s disease; (6) iron increased the non-carcinogenic health risk; (7) lead impaired neurodevelopmental functions in children; (8) manganese increased the risk of attention-deficit hyperactivity disorder (ADHD); and (9) mercury was causally related to chronic kidney disease. In contrast, for nickel and zinc, no overt health risks have been reported, likely due to low levels in the drinking water, attributable to their low water solubility. Of note is the good news that some HMs represent essential elements for human health. In essence, many HMs were detected in drinking water and exerted non-carcinogenic or carcinogenetic health risks, requiring proactive management of national and international regulatory authorities. Full article

We have developed mold matrices that can be employed to distinguish between enantiomers (D- and L-glucose) and structural isomers (n- and iso-stearic acid) in matrix-assisted laser desorption/ionization mass spectrometry. Utilizing a temperature-responsive polymer, a molecular structure recognition film was created around metal or semiconductor particles, such as silver (Ag) or cadmium telluride (CdTe), forming the core. Molecules that fit the template structure were selectively ionized. To elucidate the properties of the mold matrix, the relationship between molecular recognition rate and peak intensity of analyte ion was investigated by varying polymer film thickness around the core. The relationship between molecular recognition rate and hydrophobicity of the template molecule was also examined. It was found that increasing the amount of polymer forming the molecular recognition film improved the molecular recognition rate. However, the peak intensity of the analyte ion decreased. It was also found that using highly hydrophobic molecules as template molecules resulted in high molecular recognition rates. In addition, a water-splitting photocatalyst was synthesized and utilized to fabricate the mold matrix. It was applicable to both positive and negative ion generation while recognizing the molecular structure of the analyte. Full article

The article presents a method of measurement and a test stand for determining the specific electrical resistivity of granular carburizing materials most commonly used in foundry practice. The research was conducted for synthetic graphites (GS) and petroleum cokes (KN) using a test stand proposed by the authors of the study and protected by a patent. It was shown that this measurement method allows for a clear distinction between the tested materials. For synthetic graphites, specific resistivities in the range of 35.9–144.5 μΩ·m were obtained, while for petroleum cokes the range was 172.1–1390 μΩ·m. The main aim of the study was to determine whether there is a correlation between the measured electrical resistivity of the tested materials and the carburization efficiency obtained in melting experiments. Therefore, the article also presents the course and results of studies on the process of cast iron melting in laboratory induction furnaces, where the carburizing material was introduced into the induction furnace with a fixed charge. Carburization efficiencies obtained for synthetic graphite ranged from 86.6% to 94.4%, and from 65.5% to 85.31% for petroleum coke. Based on the measurement results, a statistical analysis was carried out, yielding a relationship with a coefficient of determination R² = 0.92. The research confirmed the possibility of a quick assessment of carburizers in terms of their assimilation degree by molten metal. This is valuable information both for scientific research and industrial applications. The presented results form part of ongoing studies aimed at explaining the differences occurring within a given group of materials (petroleum cokes and synthetic graphites). Full article

Background: Copper nanoparticles (CuNPs) are promising antibacterial agents, but instability and heterogeneity in ‘green’ routes limit translation. Methods: We developed a one-step synthesis in which pre-polymerized polycatechin acts as both reductant and capping agent to form copper–polycatechin core–shell nanoparticles (Cu@polycat). Physicochemical properties (TEM/DLS/XRD/FTIR/ζ), colloidal stability (pH, salt, serum), ion release, and antibacterial activity against planktonic and biofilm E. coli/S. aureus were evaluated. Results: Cu@polycat featured a ~21.5 nm metallic core and ~45 nm hydrodynamic diameter (shell ≈ 12 nm, estimated from TEM–DLS) with ζ ≈ −34 mV, conferring high stability across physiological conditions. Cu@polycat outperformed uncoated CuNPs, displaying 8-fold lower MICs and rapid bactericidal kinetics (>5-log10 in 6–8 h). Synergy between the copper core and polycatechin corona was confirmed (FICI ≈ 0.08). Cu@polycat inhibited biofilm formation by >80% and reduced viable counts in 24 h mature biofilms by ≥3-log10, whereas ampicillin was ineffective under the same biofilm conditions. Conclusions: A polycatechin-based green route furnishes a stable, synergistic nano-antibacterial platform with potent anti-biofilm activity, supporting development for wound-care and anti-fouling device coatings. Full article

The growing demand for environmentally friendly materials has driven extensive research into biopolymer-based nanocomposites with enhanced functional performance. Chitosan, a naturally derived polysaccharide, offers excellent film-forming ability, biodegradability, and antimicrobial potential, making it a promising matrix for sustainable packaging and coating applications. In this study, a distinctive solvent-casting strategy was employed to fabricate chitosan-based nanocomposite films functionalized with dual-action silver/titania (Ag/TiO₂) nanoparticles, combining both photocatalytic and metallic antimicrobial mechanisms—an approach that provides broader functionality than conventional single-component fillers. The biodegradable films were systematically characterized for their structural, mechanical, optical, and barrier properties, as well as their antimicrobial performance. The integration of Ag/TiO₂ imparted unique synergistic effects, modifying film morphology and color, slightly reducing tensile strength, and enhancing hydrophobicity and structural compactness. The obtained water vapor permeability values (0.013–0.102 g·mm·m⁻²·h⁻¹·kPa⁻¹) classified the materials as moderate barriers, comparable to or better than many existing chitosan-based systems without nanofiller reinforcement. Notably, films containing 10 wt% Ag/TiO₂ achieved a 40.4% reduction in Escherichia coli viability and an 8.2% inhibition of Staphylococcus aureus, demonstrating concentration-dependent antimicrobial activity superior to that of neat chitosan films. Overall, the unique combination of a biodegradable chitosan matrix with multifunctional Ag/TiO₂ nanofillers offers clear advantages over traditional biopolymer films, highlighting their potential as advanced materials for active food packaging and antimicrobial surface coatings. Full article

To prepare a high-performance Fe-based laser cladding coating, herein, various Fe60/WC/Y₂O₃ coatings are deposited on the surface of 42CrMo steel plate via a laser cladding technique. The WC dosage is fixed as 10 wt%, while the dosage of Y₂O₃ ranges from 0 to 7.5 wt%. The influences of Y₂O₃ dosage on the coating hardness, wear resistance, and corrosion resistance are investigated. With the addition of Y₂O₃, the feature peak of WC disappears, and the peaks of M₂₃C₆ gradually weaken, indicating that Y₂O₃ promotes the decomposition of WC and suppresses the formation of new metal carbides. When the dosage of Y₂O₃ is 2.5 wt%, a grid-like structure is formed on the coating surface, suggesting uniform distribution of decomposed W within the Fe matrix. When the Y₂O₃ dosage exceeds 5 wt%, a large amount of CO₂ gas is released, leading to an increase in surface pores. Through a comparison, the optimal dosage of Y₂O₃ is 2.5 wt%, and the resulting 3# coating has the highest hardness of 861.97 HV. Moreover, the 3# coating also shows the minimum friction coefficient and the minimum wear volume, reflecting its superior wear resistance. The polished coating serves as a working electrode, and the corrosion resistance is tested in 3.5% NaCl solution. The sample containing 2.5 wt% Y₂O₃ has the highest corrosion potential and the lowest corrosion current density, indicating excellent corrosion resistance. The enhanced performance is ascribed to the improved surface quality and the formation of a W-reinforced grid structure. The high-performance coating has promising application potential in material and component repair. Full article

This study systematically investigates the effect and mechanism of a TiO₂ nano-lubricant on edge cracking and surface quality during the rolling of Mg/Al composite foils. Initial friction and wear tests identified an optimal nano-lubricant concentration of 3.0 wt.%, at which the system achieved a minimum average coefficient of friction of 0.067. Subsequent rolling tests using this concentration showed that the nano-lubricant reduced rolling force by 5.39–7.54% compared to dry conditions. It also significantly suppressed the initiation and propagation of edge cracks. Furthermore, the surface roughness parameters Ra and Rz were reduced by 16.5% to 24.0%, and the height profile fluctuation range was reduced by 33% to 45%, resulting in a smoother and more uniform surface morphology. The analysis of the underlying mechanism indicates that the superior performance originates from the synergistic effects of the rolling effect, the mending effect, the polishing effect, and the protective film effect. This work establishes that the use of a 3.0 wt.% TiO₂ nano-lubricant is a viable strategy for fabricating high-quality Mg/Al composite foils with minimal defects. It thereby offers both theoretical and practical guidance for the advanced rolling of bimetallic composites. Full article

In this paper, the effects of 3D printing parameters on the metallurgical and mechanical properties of 3D-printed 25CrMo4 steel are presented. Using laser-based powder bed fusion of metals (PBF-LB/M), samples were fabricated under varying conditions of laser power, scan speed, and layer thickness. The study examined how variations in volumetric energy density (VED) and linear energy density (LED) influence the material’s performance. The results show a strong correlation between the printing parameters and key properties such as hardness, porosity, bending strength, compressive strength, and tensile strength. Appropriate VED and LED improved density, reduced defects, and enhanced mechanical performance, whereas excessive energy inputs introduced brittleness. These findings support the advancement of additive manufacturing technologies for high-strength steels and broaden their potential applications in the aerospace, automotive, and construction sectors. Full article

This study represents comprehensive research that arises from the advanced sorption properties of zwitterionic resin beads, which were tested on simulated mono- and multicomponent heavy metal ion (HMI)-polluted water, compared to the stream collected in the Tarnita mine area. Ionic exchange resins (IExRs) were first synthesized in cationic form from a highly crosslinked (8%) acrylic copolymer, by introducing different side groups containing amino functionalities, such as ethylenediamine, triethylenetetramine, and hydrazine hydrate. The corresponding zwitterionic form of each IExR was obtained by reacting the cationic resins with sodium chloroacetate. The structures and morphologies of the synthesized resins were characterized using scanning electron microscopy and infrared spectroscopy. Successful removal of Cu(II), Fe(II), and Mn(II) was quantified by using atomic absorption spectroscopy. Tests with multicomponent synthetic solutions revealed the following typical order of retention: Cu(II) > Fe(II) > Mn(II). In the case of water samples collected from the Tarnita area, the zwitterionic resins were able to retain approximately 93.8% Mn(II), 94.7% Fe(II), and >95.5% Cu(II); in all instances, the concentration of Fe(II) was significantly higher than that of Cu(II) and Mn(II). Additionally, sorption isotherms, kinetics, and thermodynamic parameters were studied. Wheat germination was included to test the efficiency of the batch sorption using IExRs, compared to the stream collected from Tarnita, highlighting how the water cleaning process leads to healthy plant growth. The results demonstrate that, after IExRs sorption the tested HMIs content is below the permissible maximum level for surface water, effectively mitigating the pollution of the steam near to the Tarnita closed mine area, removing the main contaminants found in it. Full article

The article presents the results of a study on the production of a complex chromium–manganese–silicon-containing ferroalloy in a large-scale laboratory ore-thermal furnace using man-made waste—chromium-containing aspiration dust obtained during smelting of high-carbon ferrochrome, fines (−5 mm) of iron–manganese ore currently stored in landfills, and finely dispersed coal sludge formed during enrichment. A single-stage technology for the production of a new complex chromium–manganese–silicon-containing ferroalloy by carbothermal reduction is proposed. A metallurgical assessment of the initial charge materials was carried out by the X-ray diffraction (XRD) phase analysis, and metal samples of the obtained ferroalloy were studied by scanning electron microscopy (SEM) in combination with energy dispersive spectroscopy (EDS). The resulting ferroalloy has a complex microstructure with a predominance of carbide and intermetallic phases. A high degree of extraction of chromium (up to 80%), manganese (up to 75%), and silicon (up to 35%) was recorded. The average chemical composition of the obtained ferroalloy, wt.%: Cr—37.41; Mn—17.31; Si—11.84; C—3.81; P—0.14; S—0.02. The slag formed during the smelting of the ferroalloy has satisfactory technological properties: it is characterized by good fluidity, and it actively exits the furnace by gravity. Entanglement of metal kings in the slag is not observed. The results obtained confirm the technological feasibility of the utilization of technogenic raw materials for the production of complex ferroalloys of the FeCrMnSi type. Full article