Search Results (1,050)

Phosphate rock is a vital natural resource classified by the European Commission as a critical raw material (CRM), extensively mined for its agricultural, industrial, and technological applications. While primarily used in fertilizer production, phosphate deposits also contain significant concentrations of trace metals, notably rare earth elements (REE), which are essential for renewable energy, electronics, and defense technologies. In response to growing demand, the recovery of REE from phosphate ores and processing by-products, particularly phosphogypsum (PG), has gained international attention. This review provides a comprehensive analysis of the global phosphate industry, examining production trends, market dynamics, and the environmental implications of phosphate processing. Special focus is placed on the geochemical behavior and mineralogical associations of REE within phosphate ores and industrial residues, namely PG and purification sludge. Although often treated as waste, these by-products represent underexplored secondary resources for REE recovery. Technological advancements in hydrometallurgical, solvometallurgical, and bioleaching methods have demonstrated promising recovery efficiencies, with some pilot-scale studies exceeding 70%–80%. However, large-scale implementation remains limited due to economic, technical, and regulatory constraints. The circular economy framework offers a pathway to enhance resource efficiency and reduce environmental impact. By integrating innovative extraction technologies, strengthening regulatory oversight, and adopting sustainable waste management practices, phosphate-rich countries can transform environmental liabilities into strategic assets. This review concludes by identifying key knowledge gaps and suggesting future research directions to optimize REE recovery from phosphate deposits and associated by-products, contributing to global supply security, economic diversification, and environmental sustainability. Full article

In this study, surface alloying technology based on Gas Tungsten Arc Welding (GTAW) was used to synthesize in situ NiTiTa coatings on a NiTi substrate using commercially pure Ta foils. The influence of different Ta contents (0.91, 1.42, and 2.91 at.%) on the microstructure, phase formation, hardness, corrosion resistance, and X-ray visibility of the prepared coatings were systematically studied. These results show that the NiTiTa coatings fabricated by GTAW were free of microcracks with good surface quality and superior adhesion to the NiTi substrate. The NiTiTa coatings are mainly composed of columnar austenitic NiTi (B2), and martensitic NiTi (B19’) with (Ti, Ta)2Ni precipitating at the grain boundaries. The proportion of B19’ martensite and the Ta content dissolved in the NiTi matrix increases with the increasing addition of Ta. In addition, β-Ta appeared in the coating formed with 1.42 at.% Ta and precipitated abundantly when the Ta amount was increased to 2.91 at.%. Changes in phase composition and secondary phases lead to a decrease in the material nanohardness. To simulate the body fluid environment, corrosion tests were conducted in Hank’s solution at a rate of 0.5 mV/s. Electrochemical tests show that the NiTiTa coatings exhibit superior corrosion resistance, where the corrosion potential, Ecorr, increased with increasing Ta content. The enhanced X-ray visibility of the newly formed coatings was also revealed. This work provides a cost-effective method for in situ synthesis of NiTiTa coatings on NiTi alloys, highlighting its potential for improving the corrosion resistance and X-ray visibility of NiTi shape memory alloys. Full article

Vertical slot fishways represent critical ecological migration facilitation structures and have been globally implemented to restore fish passage. However, most studies to date focus primarily on fishway hydraulics and fish behavior, with limited investigation into sediment deposition effects that may compromise functionality. To address this gap, we integrated physical modeling and numerical simulations to systematically analyze sediment deposition in a vertical slot fishway and its impacts on common carp upstream migration. Results indicate that sediment deposition raised fish vertical swimming positions by an average of 5.0 cm, thereby reducing pool activity space by 5.2–20.2%, altering flow patterns, and disrupting carp bottom-migration behavior. Consequently, carp exhibited increased exploratory behavior and directional uncertainty. Moreover, sediment-induced vertical vortices elevated fish energy consumption, decreasing upstream migration success from 89% to 48%. Multiple linear regression confirmed that average sediment deposition height significantly affects both migration rate and vertical swimming positions, whereas mean deposition slope demonstrates negligible influence. This study elucidates the multifaceted impacts of sediment deposition on fishway efficacy, providing a scientific basis for optimizing designs to enhance migration success and long-term functionality. Full article

Background: Quantifying absorbed doses from radiopharmaceuticals within human organs necessitates advanced computational modeling, as direct in vivo measurement remains impractical. Methods: In this study, three Monte Carlo-based simulation codes, Monte Carlo N-Particle version 6 (MCNP6), GEANT4 Application for Tomographic Emission (GATE), and GEANT4-based Architecture for Medicine-Oriented Simulations (GAMOS), were employed to evaluate internal dosimetry following the Medical Internal Radiation Dose (MIRD) formalism. As an illustrative case, simulations were first performed for ^99mTc-MIBI uptake in the myocardium using the anthropomorphic phantom, with the heart modeled as the source organ to assess energy deposition in key target organs. Dose assessments were conducted at two time points: immediately post-injection and at 60 min post-injection (representing the cardiac rest phase), allowing comparison against established clinical reference data. Results: Across all codes, organ-specific dose distributions exhibited strong consistency. The pancreas absorbed the highest dose (GATE: 21%, GAMOS: 20%, MCNP6: 22%), followed by the gallbladder (GATE: 18%, GAMOS: 17%, MCNP6: 18%) and kidneys (GATE: 16%, GAMOS: 15%, MCNP6: 16%). These findings established a consistent organ dose ranking: pancreas > gallbladder > kidneys > spleen > heart/liver, corroborating previously published empirical data. To demonstrate the versatility of the framework, additional simulations were performed with ¹⁸F in an anthropomorphic phantom and with spherical tumor models using therapeutic radionuclides (¹⁷⁷Lu and ²²⁵Ac). This broader application underscores the adaptability of the tri-code approach for both diagnostic and therapeutic scenarios. Conclusions: This comparative analysis highlights the complementary advantages of each Monte Carlo platform. GATE is well-suited for high-fidelity clinical applications where anatomical and physical accuracy are critical. GAMOS proves advantageous for rapid prototyping and iterative modeling workflows. MCNP6 remains a reliable benchmark tool, particularly effective in scenarios requiring robust radiation transport validation. Together, these Monte Carlo frameworks form a validated and adaptable toolkit for advancing internal dosimetry in personalized nuclear medicine, supporting both clinical decision-making and the development of safer, more effective radiopharmaceutical therapies. Full article

Samples of H13 tool steel were produced using the LENS^® laser additive manufacturing technique. Three variants of samples were produced such that during and 2 h after deposition, both the substrate and sample temperatures were maintained at 80, 180, and 350 °C. After the samples were produced, the effect of the substrate temperature on their metallurgical quality, microstructure, and mechanical properties was determined. No segregation of alloying elements was observed. The test results indicate that, depending on the temperature used, the structure of the H13 alloy is martensitic or martensitic-bainitic with a slight residual austenite content of up to 2.1%. Owing to structural changes, the obtained alloy is characterized by lower impact strength compared with conventionally produced alloys and high brittleness, particularly when using an annealing temperature of 350 °C. Isothermal annealing above the martensite start temperature results in extreme brittleness due to a partial structural transformation of martensite into bainite and probable carbide precipitation processes at the nanoscale. Full article

This research explored the technical feasibility of creating a controlled chemical composition for Fe-Ni alloys using a Directed Energy Deposition (DED) arc metal additive manufacturing (AM) process in its twin wire feed mode. This method employs two independently controlled arc power sources to feed two different wires into a single torch, creating a unified melt pool protected by a single shielding gas nozzle. The research focused on producing Invar 36 (EN 1.3912), a low thermal expansion alloy, by melting and mixing steel and Ni-Fe wires using Cold Metal Transfer-Twin (CMT-Twin) technology. This method enables the fabrication of multi-material components featuring regions with distinct chemical compositions, including functional gradients, with the aim of leveraging the advantageous properties of each individual material. Furthermore, this new manufacturing route offers the possibility to avoid using some alloying elements, such as Nb, an element considered a critical raw material (CRM) in the European Union (EU). Microstructure and mechanical properties were analyzed and compared to commercial Invar 36 obtained by DED-Arc with single wire as well as the effect of the absence of Nb. Results showed that the in situ obtained alloy had 10–20% lower strength but exhibited 10–15% higher elongation compared to the commercial alloy, making it a promising alternative for advanced manufacturing by using this new manufacturing route. Full article

Thin films of nickel oxide (NiO) were deposited on a 5° miscut magnesium oxide (MgO)(100) substrate using electron-beam evaporation to pursue morphology-directed resistive switching. The atomic force microscope (AFM) confirmed a stepped surface with a terrace width of ~85 nm and a step height of ~7 nm. After deposition, the film resistance decreased from 200 MΩ to 25 MΩ by annealing under ambient air at 400 °C, attributed to the increase in the p-type conductivity through nickel vacancy formation. Top electrodes of Ag (500 nm width, 180 nm gap) were patterned parallel or perpendicular to the substrate steps using UV and electron-beam lithography. Devices aligned parallel to the step showed reproducible unipolar switching with 100% yield between forming voltages 20–70 V and HRS/LRS~10² at ±5 V. In contrast, devices formed perpendicular to the steps (8/8) subsequently failed catastrophically during electroforming, with scanning electron microscopy (SEM) showing breakdown holes on the order of ~100 nm at the step crossings. The anisotropic electrodynamic response is due to step-guided electric field distribution and directional nickel vacancy migration, illustrating how substrate morphology can deterministically influence filament nucleation. These results highlighted stepped MgO as a template to engineer the anisotropic charge transport of NiO, exhibiting a reliable ReRAM as well as directional electrocatalysis for energy applications. Full article

It is known that the addition of SrO heterogeneous nucleation site particles can refine the microstructure of SUS316L stainless steel additively manufactured (AMed) by powder bed fusion (PBF). In this study, this idea was confirmed by directed energy deposition (DED). However, there are several types of DED machines, and the energy system and the material supply system of these machines are different depending on each machine. In this study, the grain refinement behavior and the formability of AMed SUS316L stainless steel with the addition of SrO heterogeneous nucleation site particles are evaluated using a single-beam type LAMDA 200 machine and a multi-beam type ALPION Series machine. The size of the melt pool made by the ALPION Series machine is smaller than that of the LAMDA 200 machine, which results in a shorter residence time in the liquid state of the melt pool for the ALPION Series machine. The grains formed in the inoculated sample manufactured by the ALPION Series machine under the unidirectional scanning strategy are found to be refined compared to those in the uninoculated sample. On the other hand, it is found that the formation of defects and the crystallographic texture observed in the samples manufactured by the LAMDA 200 machine is suppressed by the addition of SrO heterogeneous nucleation site particles. These differences between the ALPION Series and LAMDA 200 machines would come from the differences in the melting state, including temperature, cooling conditions, and re-heating. Full article

The synthesis of thin films in multilayer structures on different textiles is of interest due to their potential use in flexible solar absorber coatings and thin-film solar cells. The aim of the study was to deposit bismuth(III) sulphide and copper(II) sulphide thin films on various textiles at the same time. This was achieved using the sustainable and cost-effective successive ionic layer adsorption and reaction (SILAR) method. The study examined how the elemental distribution, phase composition, crystallinity, surface morphology, and optical features of the resulting films are determined by the intrinsic structure and material makeup of structural textiles. The analysis used data from scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD), as well as ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy. Depending on the textiles used, the formed films were polycrystalline and rich in copper. According to the findings, the normalised atomic percentages were as follows: Cu, 57.66–68.75%; Bi, 1.19–5.26%; S, 30.06–38.63%. The direct transition optical energy gap values varied from 1.3 to 2.88 eV, while the indirect varied from 0.9 to 2.25 eV, and the refractive index from 1.3 to 1.8. These properties were influenced by the composition of the textiles and the films themselves. These properties directly impact the films’ applications. Full article

In this study, supercritical carbon dioxide (scCO₂) was investigated as a sustainable medium for cotton yarn sizing and desizing, eliminating the need for water and conventional organic solvents. Cellulose acetate was employed as the sizing agent with acetone as a co-solvent, achieving a 10% add-on comparable to conventional starch-sized yarns. Since starch sizing is typically reported in the range of 3–10% add-on, a 3% starch level was selected as the industrially relevant benchmark for 20/1 cotton yarn. Trials conducted at 15–20 MPa and 40–60 °C demonstrated uniform size deposition and efficient removal during desizing, as confirmed by weight gain distribution and friction testing. Mechanical characterization further revealed that scCO₂-sized yarns exhibited tensile strength and break elongation within the range of industry benchmarks. Overall, these findings establish scCO₂-based sizing as a viable and eco-friendly alternative, with encouraging preliminary performance that suggests potential alignment with textile industry standards. The process also shows promise for solvent recovery and effluent reduction; however, full quantification of recovery yields, energy requirements, and wastewater impacts remains an important direction for future investigation. Full article

The laser-directed energy deposition (L-DED) technique, with its excellent environmental adaptability and superior repair capability, shows great potential for the repair of damaged X70 pipeline steel. In this work, the microstructure and mechanical properties of L-DED repaired X70 steel were systematically investigated. The deposited material exhibited inhomogeneity along the building direction. From the bottom to the top, the grains gradually coarsened, and the proportion of polygonal ferrite increased. This was mainly attributed to increasing thermal accumulation with deposition height, which reduced the cooling rate and promoted solid-state transformations at higher temperatures. Meanwhile, the heat accumulation and intrinsic heat treatment reduced the dislocation density and promoted Fe₃C precipitation within grains and along boundaries. Microhardness was highest in the bottom region and decreased along the building direction due to the gradual coarsening of microstructure and decreasing in dislocation density. The L-DED X70 showed lower yield strength (435 MPa) and ultimate tensile strength (513 MPa) compared to the base material and API 5L requirements. The elongation of the L-DED X70 was 42.9%, which was 58% higher than that of the base material, indicating excellent ductility. These results revealed a thermal history-dependent strength–ductility trade-off in the L-DED repaired X70 steel. Therefore, more efforts are needed to control the L-DED thermal process, tailor the microstructure, enhance strength, and meet the service requirements of harsh environments. Full article

Material Extrusion for Metals (MEX/M) has emerged as a cost-effective and versatile Additive Manufacturing technology (AM) for producing complex metal components. Despite its potential, parts realized via MEX/M suffer from significant limitations, primarily poor surface quality due to the intrinsic layer-wise effect from the printing deposition and selected printing conditions. Furthermore, the multi-step nature of the MEX/M process, particularly the sintering stage, can exacerbate roughness along with the printing orientation, thereby affecting part performance and limiting potential applications. In addition to surface defects, MEX parts are characterized by a high content of porosity when compared to other metal AM technologies like Powder Bed Fusion laser-based (PBF-LB) and Directed Energy Deposition laser-based (DED-LB). These defects, both on the surface and within the parts, can compromise the mechanical properties and overall quality of the final parts. In this context, the scientific community has increasingly recognized post-treatment processes as essential for simultaneously improving surface quality and enhancing bulk material properties. This review according to the PRISMA 2020 guidelines provides a comprehensive analysis of the most critical post-treatment processes applied to MEX/M parts. By critically reviewing the state of the art, this paper discusses how these treatments can effectively mitigate outer and inner defects, reduce porosity, and significantly improve mechanical performance, ultimately enabling the broader industrial adoption of MEX/M technology. Full article

The impingement of a molten droplet on a solid surface, forming a “splat,” is a fundamental phenomenon observed across numerous industrial surface engineering techniques. For example, thermal spray deposition is widely used to create metal, ceramic, polymer, and composite coatings that are vital for aerospace, biomedical, electronics, and energy applications. Significant progress has been made in understanding droplet impact behavior, largely driven by advancements in high-resolution and high-speed imaging techniques, as well as computational resources. Although droplet impact dynamics, splat morphology, and interfacial bonding mechanisms have been extensively reviewed, a comprehensive overview of the mechanical behaviors of single splats, which are crucial for coating performance, has not been reported. This review bridges that gap by offering an in-depth analysis of bonding strength and residual stress in single splats. The various experimental techniques used to characterize these properties are thoroughly discussed, and a detailed review of the analytical models and numerical simulations developed to predict and understand residual stress evolution is provided. Notably, the complex interplay between bonding strength and residual stress is then discussed, examining how these two critical mechanical attributes are interrelated and mutually influence each other. Subsequently, effective strategies for improving interfacial bonding are explored, and key factors that influence residual stress are identified. Furthermore, the fundamental roles of splat flattening and formation dynamics in determining the final mechanical properties are critically examined, highlighting the challenges in integrating fluid dynamics with mechanical analysis. Thermal spraying serves as the primary context, but other relevant applications are briefly considered. Cold spray splats are excluded because of their distinct bonding and stress generation mechanisms. Finally, promising future research directions are outlined to advance the understanding and control of the mechanical properties in single splats, ultimately supporting the development of more robust and reliable coating technologies. Full article

Effective thermal management is essential in metal additive manufacturing to ensure process stability and desirable material properties. Directed energy deposition using a laser beam and wire (DED-LB/w) enables the production of large, high-performance components but remains sensitive to adverse thermal effects during multi-layer deposition due to heat accumulation. While prior studies have investigated interlayer temperature control and substrate preheating in DED modalities, including laser-powder and arc-based systems, the influence of substrate preheating in DED-LB/w has not been thoroughly examined. This study employs substrate preheating to simulate heat accumulation and assess its effects on melt pool geometry, wire–melt pool interaction, and the microstructural evolution of Alloy 718. Experimental results demonstrate that increased substrate temperatures lead to a gradual expansion of the melt pool, with a notable transition occurring beyond 400 °C. Microstructural analysis reveals that elevated preheat temperatures promote coarser secondary dendrite arm spacing and the development of wider columnar grains. Moreover, Nb-rich secondary phases, including the Laves phase, exhibit increased size but relatively unchanged area fractions. Observations from electrical conductance measurements and coaxial visual imaging show that preheat temperature significantly affects the process dynamics and microstructural evolution, providing a basis for advanced process control strategies. Full article

The decline in eggshell quality of aged laying hens represents a major economic challenge in poultry production. While a 28 h ahemeral light cycle has been shown to improve eggshell quality, its underlying mechanism remains unclear. This study randomly assigned 260 74-week-old Hy-Line Brown laying hens to two light cycle groups, a normal 24 h cycle group (16L:8D) and a 28 h ahemeral cycle group (16L:12D). Each treatment comprised 130 hens divided into two replicate groups. The trial lasted 16 weeks. We systematically analyzed circadian rhythms of gut microbiota and serum metabolites using 16S rRNA sequencing and untargeted metabolomics. Compared with the 24 h cycle, the 28 h cycle significantly enhanced eggshell thickness by 0.04 mm and 0.02 mm, and eggshell strength by 4.19 N and 4.76 N at 79 and 84 wk, respectively. Mechanistically, the 28 h light cycle remodeled the circadian rhythms of gut microbiota, increasing their richness and diversity, and altered the rhythmic patterns of serum metabolites. We identified nine microbial genera and three hundred seventy metabolites that exhibited opposite rhythmic patterns under the two light cycles. These changes were primarily enriched in pathways related to amino acid, carbohydrate, lipid, and energy metabolism. Correlation analysis further revealed strong associations between key microbes and functional metabolites. Weissella promotes calcium deposition in eggshells through synergistic interactions with calcium chelators such as gluconic acid and threonine acid. Meanwhile, YRC22 and Paludibacter synergistically support membrane formation substances, thereby promoting the proliferation of uterine epithelial cells and eggshell formation. Our findings indicate that the 28 h ahemeral light cycle improved eggshell quality in aged hens by remodeling the circadian rhythms of gut microbiota and metabolites, thereby synergistically enhancing calcium ion absorption and uterine tissue health. This provides a novel theoretical basis and practical direction for improving late-phase egg quality through light management strategies. Full article