Search Results (972)

The purpose of this study is the exploration of the catalytic performance of a ZSM-5 zeolite produced from iron-rich fly ash, without any additional iron loading, in removing paracetamol via a heterogenous Fenton reaction. The structural and textural characterization by powder X-ray diffraction and N₂ adsorption isotherms showed that a pure ZSM-5 phase was synthesized, but lower crystallinity and textural parameters were obtained when compared with commercial ZSM-5. The XPS analysis revealed significant amounts of iron and yttrium, which enhanced the electronic properties of the samples’ surface when compared with iron-impregnated commercial ZSM-5. The catalytic reaction was followed through UV-spectroscopy and kinetic models were applied to the data; the best fit was obtained for a pseudo-first-order model. All fly ash-based zeolites showed increased paracetamol removal when compared with commercial iron-loaded ZSM-5, which may be attributed to the more disordered structure, able to accommodate large paracetamol species (dimers). On the other hand, the effect of yttrium on the electronic properties of iron sites may increase the ^●OH radical formation, thus increasing the paracetamol removal rate, despite the progressive drop on paracetamol removal upon regeneration–reuse cycles due to Fe leaching. Full article

We report on sub-50 fs pulse generation from a diode-pumped mode-locked laser based on an ytterbium-doped monoclinic potassium yttrium double tungstate crystal operating in the 1 μm spectral region. Pumping by a low-power, spatially single-mode, fiber-coupled laser diode at 976 nm, a maximum continuous-wave output power of 433 mW at 1066.1 nm was obtained. Using a quartz-based intracavity Lyot filter, an exceptionally broad continuous-wavelength tuning range of 98 nm was achieved. In the mode-locked regime, the diode-pumped Yb:KY(WO₄)₂ laser delivered soliton pulses as short as 46 fs at a central wavelength of 1069.2 nm by employing a SEmiconductor Saturable Absorber Mirror. To the best of our knowledge, these results represent the broadest continuous-wave tuning range and the shortest pulse duration ever reported for lasers based on ytterbium-doped monoclinic double tungstate crystals. Full article

A holmium-doped yttrium aluminum garnet (Ho:YAG) thin disk was experimentally investigated under Q-switching and cavity-dumping operation schemes, pumped by a 1.9 µm laser diode (LD). The laser generated pulses at 2090 nm with energies more than 6 mJ and pulse duration down to 3.8 ns, corresponding to a peak power of 1.6 MW with near-diffraction-limited beam quality. The compact and robust system was used for laser-induced breakdown spectroscopy (LIBS) experiments, demonstrating its practical usability. These results represent, to the best of our knowledge, the first demonstration of a Ho:YAG thin-disk laser providing MW peak power in the nanosecond regime. Full article

The disposal of end-of-life fluorescent lamps presents significant environmental challenges due to their mercury (Hg) content and the loss of valuable rare earth elements (REEs) contained in phosphor powders, highlighting the need for sustainable recycling strategies. This study proposes an integrated hydrometallurgical process for simultaneous mercury removal and material recovery from spent fluorescent lamps. Various leaching agents were initially evaluated for mercury dissolution, and 10% NaOCl was identified as the most effective solution. The optimized system was applied to linear T8 lamps using a combined milling–leaching approach, followed by size-based separation of metallic, glass, and phosphor fractions. Dissolved mercury was precipitated at pH 11 using Na₂S, forming crystalline α-HgS (cinnabar), as confirmed by XRD, and reducing the residual mercury concentration to 2.7 µg/L. The metallic fraction was recovered as an aluminum-based alloy containing 20.6 wt.% Cu and 10.9 wt.% Zn with low iron content, while the phosphor-rich fraction yielded approximately 50% REE extraction, followed by oxalate precipitation of yttrium-based compounds. The developed process enables efficient mercury stabilization and selective recovery of valuable materials, supporting environmentally secure and resource-efficient fluorescent lamp recycling. Full article

A detailed numerical optimization of side-pumped cerium- and neodymium-codoped yttrium aluminum garnet (Ce:Nd:YAG) solar laser architectures was performed using Zemax^® and LASCAD^TM, aiming for both high-power multimode and TEM₀₀-mode performances. Multiple rod configurations and laser resonator geometries were evaluated to maximize absorbed pump power, improve mode overlap, and ensure thermal stability. For multimode operation, the optimal design was a four-rod cross side-pumped configuration employing 4.0 mm diameter, 25 mm length rods, which numerically delivered a solar laser output power of 134 W (resulting in a collection efficiency of 49.1 W/m² and solar-to-laser conversion efficiency of 4.91%), representing a 1.50-times improvement over the best previously reported value of 89.29 W. For TEM₀₀-mode generation, the best performance was obtained with a three-rod horizontal side-pumped configuration using 2.5 mm diameter, 34 mm length rods, achieving a collection efficiency of 21.1 W/m² and solar-to-laser conversion efficiency of 2.11%, surpassing the record 16.49 W/m² reported in earlier literature. Thermal analyses revealed low peak temperatures, reduced thermally induced stress, and minimized refractive-index gradients in both architectures, confirming that multirod side pumping significantly improves the thermal environment and enables stable operation at high absorbed pump powers. These results demonstrate that carefully engineered multirod geometries can simultaneously enhance collection efficiency, beam quality, and thermal robustness, highlighting multirod side-pumped solar lasers as a promising pathway for further power scaling and next-generation high-performance solar laser systems. Full article

We report, for the first time, waimirite-(Y) in Egypt. This is only the third reported occurrence of this mineral in the world. This observation arose during our study of the rare earth element (REE) mineralization associated with the Neoproterozoic rare-metal granite intrusion in Wadi Abu Rusheid in the Eastern Desert of Egypt. The principal lanthanide and yttrium (Y) hosts in the area are waimirite-(Y) and bastnäsite-(Ce) in leucogranite and bastnäsite-(Y) in adjacent metasedimentary country rock. The leucogranite is a strongly fractionated, metaluminous to weakly peraluminous (A/CNK = 0.98–1.03), medium- to high-K calk-alkaline I-type granite. The metasediments are composed of upper greenschist to lower amphibolite-grade biotite schists with variable amounts of amphibole, graphite, and garnet. Leucogranite contains accessory Li-bearing mica, garnet, zircon, fluorite, and columbite in addition to the REE minerals. It is enriched by three orders of magnitude relative to primitive mantle in Li, Rb, Th, Ta, Nb, Pb, U, and Sn; relative to these highly enriched elements the concentrations of Sr, Ba, Ga, Zr, Hf, and Y are notably low. The REE patterns of most samples show strong enrichment in heavy relative to light REE but occasional samples have light REE-enriched patterns controlled by accessory REE minerals, and all display strong negative Eu anomalies (Eu/Eu* ≤ 0.05). The whole-rock chemistry of the metasedimentary units are different; relative to average upper continental crust they show enrichments of one to two orders of magnitude in Li, Rb, Pb, Sn, Cs, and sometimes Cr and Zn. The REE patterns of the metasedimentary units are nearly flat, with some samples showing negative Eu anomalies. Waimirite-(Y), nominally YF₃, also contains several weight percent each of Yb, Dy, and Er. The empirical formula (based on one cation) is (Y_0.55Ce_0.02Pr_0.01Nd_0.02Sm_0.02Gd_0.02Dy_0.05Er_0.04Yb_0.05Th_0.05Ca_0.16Pb_0.01)_∑1.00(F_2.48O_0.52)_∑3.00. Bastnäsite-(Ce) in leucogranite samples, nominally Ce(CO₃)F, also has several weight percent each of Nd₂O₃ and La₂O₃. The REE host in metasedimentary rocks is bastnäsite-(Y), nominally Y(CO₃)F, but also rich in Nd₂O₃ (11–19 wt.%) and La₂O₃ (4–14 wt.%). It is intimately associated with fluorophlogopite. The geochemical, mineralogical, and textural evidence indicates that waimirite-(Y) and bastnäsite-(Ce) in leucogranite crystallized from granite-derived F- and CO₂-bearing hydrothermal fluids, whereas the source of Y for growth of the bastnäsite-(Y) in the metasedimentary rocks is unclear; the large negative Ce anomaly in bastnäsite-(Y) suggests an oxidizing supergene setting. Despite their proximity, if there is a genetic connection between the mineralization in the granite and in its country rocks, the relationship is not evident from elemental patterns or host mineralogy. Full article

In this study, the occurrence and leachability of rare earth elements and yttrium (REY) in medium-rank coal—meta-bituminous B coal from the southwestern part of the Upper Silesian Coal Basin in Poland—were investigated. The coal samples contained variable amounts of siderite, dolomite, calcite, kaolinite, illite, quartz, apatite, and pyrite in their mineral composition. A five-step sequential chemical leaching procedure was used, including deionized water, 3% HCl, 5% HNO₃, 10% HNO₃ with microwave assistance, and concentrated HCl–HF also with microwave assistance. The highest concentrations of ∑REY were observed in seam 404/1. Light REY (LREY) dominated the REY composition (>75%), while heavy REY (HREY) accounted for less than 10%. The chondrite-normalised REY patterns and total REY content indicate a clastic origin of REY-bearing minerals. The most efficient leaching occurred in stages IV and V. The solutions from stages I–III preferentially mobilised critical REY, while those from stages IV–V reflected the REY distribution in the coal. Based on the C_outl index, both coal and leachates from the later stages are classified as prospective REY resources. However, absolute REY concentrations should be considered when interpreting C_outl values. The positive correlation between apatite and kaolinite contents and ∑REE concentrations suggests their role in REY enrichment. Full article

This editorial consists of a synopsis of the research in the Special Issue on “Superconductors and Magnetic Materials”, specifying the studies and highlighting main results and conclusions. This collection of research (1) demonstrates the possibility of notably decreasing AC losses by replacing the copper encapsulation of rare Earth barium copper oxide tapes with strong magnetic encapsulation; (2) predicts typical gains expected from soft-magnet and superconductor flux concentrators for low magnetic field sensing; (3) reveals that the n-value surfaces of high-Tc tapes can be estimated with a high accuracy using feed-forward deep neural network learning; (4) predicts the detection of a monopole plasma phase in high-Tc iron-based superconductors with a Tc above 70 K; and (5) proposes an analytical model to accurately predict the gap-to-Tc ratio for yttrium hydrides at high pressures. Full article

Thermal barrier coatings (TBCs) are an effective means of providing thermal insulation and protecting the hot-section components of gas turbine engines. Their quality and performance characteristics largely depend on the microstructural features and the bond strength between the bonding layer and the substrate. The present study aims to determine the optimal plasma spraying parameters that ensure the formation of NiCrAlY coatings with superior microstructural integrity and adhesion strength. The objective of the study is a thermally sprayed nickel–chromium–aluminum–yttrium (NiCrAlY) bond coat deposited onto an Inconel 718 nickel-based superalloy, which is widely used in aircraft gas turbine engines due to its high strength and excellent oxidation resistance at elevated temperatures. It was found that the coating produced under the optimized conditions exhibited a significantly higher adhesion strength compared with the samples obtained under other spraying regimes. The results confirm that a precise adjustment of the atmospheric plasma spraying (APS) process parameters, taking into account the equipment configuration, allows for a substantial improvement in coating quality and performance. Full article

In thermal power plants, fly ash produced from coal combustion is a solid waste that requires large storage areas and poses environmental risks. In addition, coal ash can contain significant amounts of critical elements, including rare earth elements and yttrium (REY). Despite high supply risks, demand for REY is increasing in parallel with technological developments. Therefore, the recovery of REY from coal ash is becoming increasingly important for both solid waste disposal and as a raw material source. This study presents an integrated geochemical assessment of REY in fly ashes from coal-fired thermal power plants in Türkiye, based on systematically compiled and harmonised datasets. The REY concentration of fly ash varies between 134.00 and 429.48, with an average of 230.06 ppm. Light REY are predominant in all samples. The proportion of critical REY averages 34.75, with the highest value calculated at 42% in fly ash from the Yatağan thermal power plant. While most fly ashes show L-type enrichment, there are also samples showing M-type and H-type enrichment. According to initial national-scale estimates, coal fly ashes in Türkiye may contain approximately 3.7–5 kt of rare earth oxides per year. Despite their low REY content, Turkish fly ashes can be considered a potential source for REY recovery when considering the large waste volume, in conjunction with an integrated evaluation strategy. This study establishes a geochemical basis for future process-oriented and recovery-focused investigations. Full article

A Ti6Al4V alloy fabrication via laser powder bed fusion (L-PBF) leads to the formation of coarse columnar β grains that give rise to anisotropic mechanical properties and inadequate strength. Incorporating the rare-earth oxide, yttrium oxide (Y₂O₃), has proven an effective strategy in enhancing the mechanical performance of Ti6Al4V alloys. Nevertheless, the critical Y₂O₃ content required to achieve an optimal strength–ductility balance in L-PBF Ti6Al4V has not been systematically determined. To address these critical gaps, this study, for the first time, systematically investigates the effect of various Y₂O₃ contents on the microstructural evolution and mechanical properties of Ti6Al4V alloys fabricated via L-PBF. The results demonstrate that a Y₂O₃ addition of 0.2 wt.% produces β grains and α phases with average sizes of 61.6 and 7.6 μm, respectively. Transmission electron microscopy observations reveal that Y₂O₃ nanoparticles, together with elemental Y nanoparticles formed by reduction, are distributed both within the α-Ti matrix and along phase boundaries. This distribution effectively reinforces grain boundaries and promotes heterogeneous nucleation, thereby refining the microstructure. Mechanical property tests indicate that the alloy strength significantly improves as the Y₂O₃ content increases. Specifically, the alloy with 0.2 wt.%Y₂O₃ exhibits a tensile strength of 1106 MPa, a yield strength of 1074 MPa, and an elongation of 10.7%. This study proposes an innovative rare-earth strengthening method for refining the microstructure of L-PBF-fabricated titanium alloys and comprehensively enhancing their mechanical properties. Full article

Background/Objectives: The purpose of this study was to investigate the laser removal of implant-supported ceramic single crowns, focusing on their efficiency and the potential reusability of the removed restorations. Methods: Sixty single crowns made of lithium disilicate were adhesively bonded to prefabricated titanium abutments in a total of six test series (n = 10). The test series were divided according to the different spacer settings of the crowns (90 µm, 120 µm, 150 µm) and the taper of the abutments (4°, 6°). After seven days of storage in distilled water, the single crowns were removed using an erbium-doped yttrium aluminium garnet (Er:YAG) laser. The number of laser pulses needed and the time required to remove the crowns were recorded. This was followed by a micro- and macroscopic score evaluation of the crowns using a fluorescent penetration method. Results: Laser removal of all sixty crowns was successfully performed. Using a taper of 6° and a spacer of 150 µm, the crowns were removed with significantly fewer pulses (61.40 (±36.78)). The taper and spacer had a significant effect on both the microscopic (p = 0.040) and macroscopic (p = 0.035) fracture patterns. Based on the final score of the fracture analysis, 44 of the 60 crowns could be classified as potentially reusable. The remaining 16 crowns failed due to purely macroscopic (7), purely microscopic (6), and combined microscopic and macroscopic (3) fracture behavior. Conclusions: Based on the results of this study, increasing the size of the taper and spacer has proven beneficial for laser removal in terms of time efficiency and non-destructive removal of crowns. Full article

Understanding the interactions of nanomaterials with complex tumour models is essential for advancing their use in nanomedicine. Calcium fluoride nanoparticles doped with neodymium and yttrium (CaF₂:Nd³⁺,Y³⁺) exhibit promising properties for biomedical applications, particularly for optical sensing and tagging. This study investigates their interaction with 3D cell spheroids derived from breast cancer, from Michigan Cancer Foundation-7 (MCF-7) and brain cancer, from Uppsala 87 Malignant Glioma (U-87 MG) cell lines as tumour models. Specific protocols have been developed in Total-reflection X-Ray Fluorescence (TXRF) to evaluate nanoparticles’ internalisation and diffusion within spheroids by quantifying the concentrations of Ca, Nd, and Y taken up by the cells. Minimal background interference enabled precise multi-element detection in low-volume biological samples, yielding very low detection limits and minimal uncertainties. The study demonstrates the effectiveness of TXRF for quantifying rare-earth-doped nanoparticles in 3D cancer models and reveals that, although both cell lines permit nanoparticle diffusion into cells, higher accumulation is observed in glioblastoma cell spheroids. A Weibull diffusion model was applied to help understand the observed internalisation kinetics of nanoparticles into U-87 MG and MCF-7 spheroids. The relevant differences suggest cell-line-dependent uptake behaviour, potentially influenced by differences in cellular architecture, the porosity of the generated spheroid, and its intercellular 3D microstructure. These findings highlight the importance of tumour-specific interactions in the investigation of nanoparticle systems for targeted cancer diagnostics and therapeutics. Full article

High-temperature gas-cooled reactors (HTGRs) employ spherical fuel elements containing thousands of tristructural-isotropic (TRISO) particles, each centered on a UO₂ fuel kernel. The internal gelation process is a key technology for preparing these UO₂ fuel kernels. However, its application is limited by the poor room-temperature stability of conventional broths and the inherent trade-off between broth stability and mechanical strength. In this work, a novel five-component broth system composed of ZrO(NO₃)₂, hexamethylenetetramine (HMTA), urea, acetylacetone (ACAC), and glucose was developed. The synergistic effects of ACAC and glucose on broth stability and gelation kinetics were systematically investigated. An optimal ACAC/glucose molar ratio of 1:1 and an ACAC/ZrO₂⁺ ratio of 1.5 yielded a zirconium broth stable for over 5 h at 25 °C. Yttrium-stabilized zirconia (YSZ) microspheres prepared under optimized conditions exhibited excellent sphericity (1.04 ± 0.01), high density (5.84 g/cm³), and a crushing strength of 8.0 kg sphere⁻¹. Importantly, this stabilization strategy was successfully extended to the uranium broth, increasing its room-temperature stability from minutes to 6 h. The results demonstrate that the synergistic stabilization strategy effectively decouples the trade-off between broth stability and mechanical strength during the internal gelation process, providing an energy-efficient, scalable route for the preparation of nuclear fuel microspheres. Full article

Background: Low-level laser irradiation (LLLI) can promote wound healing. However, the biological effects of the erbium-doped yttrium aluminum garnet (Er:YAG) laser on gingival wound healing remain unclear. Objectives: To assess the effects of low-level Er:YAG laser irradiation on endothelial cell activity in vitro and on early phase gingival wound healing in vivo. Methods: In vitro, human umbilical vein endothelial cells were irradiated with a low-level Er:YAG laser (30 mJ/pulse, 10 Hz, 20 and 30 s, defocused, no water spray) and assessed for viability, cytotoxicity, and migration. Standardized bilateral wounds (4 × 1 mm) were created in the palatal gingiva of 14 male mice using a scalpel and curette. The wounds were irradiated for 20 s under the same irradiation settings, using a contact tip (diameter 800 μm) to induce superficial blood surface coagulation, while contralateral sites were assigned to controls in a split-mouth design. Postoperative wound area and mRNA expression of IL-6, TNF-α, VEGF, FGF-2, and TGF-β1 were analyzed after 48 h. Results: In vitro, LLLI significantly enhanced cell proliferation with/without increasing cytotoxicity. In the wound healing assay, the LLLI significantly promoted cell migration compared with the control. In vivo, the reduction in residual wound area in the laser group was comparable to that in the control group. IL-6 and TNF-α expressions were significantly downregulated, whereas VEGF was significantly upregulated in the laser group. Conclusions: Low-level Er:YAG laser irradiation enhances anti-inflammatory and pro-angiogenic effects, suggesting its potential in promoting gingival wound healing. Full article