Search Results (11)

The reverse water–gas shift (RWGS) reaction serves as a highly flexible and critical pathway for converting CO₂ into CO, with Pt-based catalysts having been widely investigated. Here, a series of platinum-rare earth (RE) subnanometric bimetallic clusters (SBCs) were successfully prepared on carbon support by the potassium vapor reduction method. Their structure and electronic properties, along with catalytic performance, were systematically characterized and evaluated. The Pt-RE SBC catalysts exhibited excellent catalytic activity, maintaining CO selectivity above 95% at high CO₂ conversion levels and demonstrating stable operation over 100 h at 600 °C. Furthermore, the influence of different supports (carbon black and CeO₂) on the catalytic performance was compared. It was found that Pt-Sc SBCs supported on the carbon exhibited better dispersion, smaller particle size, and superior catalytic performance relative to the CeO₂ supported counterpart. This study provides new insights into the design of highly efficient and stable RWGS catalysts, highlighting the key role of the Pt-RE SBC interface synergistic effect and support selection, which is of great significance for the resource utilization of CO₂. Full article

The Apuseni-Banat-Timok-Srednogorie Metallogenic Belt is one of the most important polymetallic metallogenic belts in the western segment of the Tethys, where numerous porphyry-type, skarn-type, and epithermal deposits are developed. However, scholars have noted a lack of systematic chronological and geochemical studies of andesites within this belt. Furthermore, the metallodynamic mechanisms controlling mineralization—such as oceanic plate exhumation and plate tearing—remain controversial. To complement the available research, this study focuses on andesites from the Čukaru Peki area in Serbia and integrates zircon U-Pb dating, molybdenite Re-Os isotopic analysis, and whole-rock geochemical analysis. The results reveal that plagioclase andesitic breccia and fine-grained plagioclase amphibole andesite were emplaced during the Late Cretaceous. Consistently, the molybdenite isochron age (81.46 ± 0.60 Ma, MSWD = 1.30) constrains the mineralization event to the same period. Both rock types exhibit geochemical signatures typical of island arc volcanic rocks, characterized by high SiO₂ contents and low Al₂O₃, MgO, and TiO₂ contents, as well as pronounced fractionation between light and heavy rare earth elements (LREEs and HREEs). The magma source is the mantle wedge metasomatized by fluid-rich melts derived from the dehydration of the subducted oceanic crust. Additionally, the primary magma produced by partial melting of this metasomatized mantle wedge assimilated and was contaminated by continental crustal material predating the Vardar Ocean’s closure during its ascent. Our findings suggest that the regional andesites are products of the exhumation of the Vardar Ocean. This study aims to provide a theoretical foundation for mineral exploration in the Timok ore cluster and, simultaneously, support the identification of ore prospecting targets in andesite alteration zones. Full article

Microstructural analysis of hot-compressed magnesium alloys is crucial for understanding the plastic formability of magnesium alloys during thermo-mechanical processing. Thermal compression tests and finite element simulations were conducted on a low rare-earth (RE) Mg-1.8Nd-0.4Zr-0.3Ca alloy. Multiple microstructural characterization techniques were employed to analyze slip systems, twinning mechanisms, dynamic recrystallization (DRX), and precipitate phases in the hot-compressed alloy. The results demonstrated that the equivalent strain distribution within compressed specimens exhibits heterogeneity, with a larger equivalent strain in the core. After thermal compression, the original microscopic structure formed a necklace-like structure. The primary DRX mechanisms comprise continuous dynamic recrystallization (CDRX), twin-induced dynamic recrystallization (TDRX), and particle-stimulated nucleation (PSN). Pyramidal slip and recrystallization constitute primary contributors to peak texture weakening and tilting. Mg₄₁Nd₅ and α-Zr phases enhanced dislocation density by impeding dislocation motion and promoting cross-slip activation. Hot compression provided the necessary thermal activation energy and stress conditions for solute atom diffusion and clustering, triggering dynamic precipitation of Mg₄₁Nd₅ phases. Full article

Organometallic rare-earth complexes have attracted considerable attention in recent years due to their unique structures and exceptional magnetic properties. In this study, we report the synthesis and magnetic characteristics of a family of monopentamethylcyclopentadienyl-coordinated trinuclear rare-earth hepta-chloride clusters [(Li(THF)(Et₂O))(Cp^*RE)₃(μ-Cl)₄(μ₃-Cl)₂(μ₄-Cl)] (RE₃: RE =Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp* = pentamethylcyclopentadienide). These clusters were synthesized by reacting LiCp* with RECl₃ in a 1:1 molar ratio within a mixed solvent system (THF: Et₂O = 1:9), resulting in high solubility in common organic solvents such as DCM, THF, and Et₂O. Magnetic studies conducted on these paramagnetic clusters reveal the coexistence of ferromagnetic and antiferromagnetic superexchange interactions in Gd₃. Additionally, Dy₃ exhibits both ferromagnetic and antiferromagnetic intramolecular dipolar interactions. Notably, slow magnetic relaxation was observed in Dy₃ below 23 K under a zero DC applied field with an energy barrier of 125(6) cm⁻¹. Full article

Metal–organic frameworks (MOFs) have emerged as promising catalysts in the hydrogenation of bicyclopentadiene (DCPD) and furfural. The physical adsorption behaviors of substrate molecules and H₂ within the pore structures of MOFs significantly influence the efficacy of subsequent catalytic reactions. This study employs molecular dynamics (MD) simulations to identify the optimal temperature and pressure conditions for the adsorption of DCPD and H₂, as well as furfural and H₂, within rare-earth-element-based MOFs (RE-MOFs). By analyzing the physical adsorption characteristics of 1538 RE-MOFs, we investigate the correlation between pore structures and adsorption capabilities. This exploration has led to the identification of 10 RE-MOF structures that demonstrate superior physical adsorption performance for both DCPD and furfural. Following this initial evaluation, density functional theory (DFT) calculations were conducted to determine the chemisorption energies of H₂ molecules on these 10 selected RE-MOF structures. Notably, the structure identified as “JALLEQ_clean” exhibited the most optimal overall adsorption performance. This study elucidates the quantitative relationship between the pore structure of RE-MOFs and their physical adsorption performance, clarifying the influence of porosity parameters on adsorption capacity and highlighting the advantages of cluster-type structures in mass transfer and adsorption. The findings provide theoretical guidance for developing high-performance RE-MOF catalysts and offer new insights for the rational design of MOF-based catalytic materials. Full article

Tuning a material’s hydrophobicity is desirable in several industrial applications, such as hydrocarbon storage, separation, selective CO₂ capture, oil spill cleanup, and water purification. The introduction of fluorine into rare-earth (RE) metal–organic frameworks (MOFs) can make them hydrophobic. In this work, the linker bis(trifluoromethyl)terephthalic acid (TTA) was used to make highly fluorinated MOFs. The reaction of the TTA and RE³⁺ (RE: Y, Gd, or Eu) ions resulted in the primitive cubic structure (pcu) exhibiting RE dimer nodes (RE-TTA-pcu). The crystal structure of the RE-TTA-pcu was obtained. The use of the 2-fluorobenzoic acid in the synthesis resulted in fluorinated hexaclusters in the face-centered cubic (fcu) framework (RE-TTA-fcu), analogous to the UiO-66 MOF. The RE-TTA-fcu has fluorine on the linker as well as in the cluster. The MOFs were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and contact angle measurements. Full article

This work investigates the microstructure and inclusions of a compacted graphite iron (CGI) alloyed by Ce and La rare earth (RE) elements. In our study, alloying elemental distribution and solute segregation were characterized by methods of secondary ion mass spectrometry (SIMS) and a three-dimensional atom probe (3DAP) with high sensitivity and spatial resolution. RE sulfide, MgS, carbide, and composite inclusions formed during solidification and provided heterogeneous nucleation cores for the nucleation of the graphite. Significant solute clustering in the matrix, coupled with the segregation of solute to grain boundaries, was observed. C, Mn, Cr, and V were soluted in cementite and promoted the precipitation of cementite, while Si was found to be soluted in ferrite. Cu is usually distributed uniformly in ferrite, but some Cu-rich atom clusters were observed to segregate towards the interface between the ferrite and cementite, stabilizing the pearlite. In addition, P, as a segregation element, was enriched along the boundaries continuously. The RE elements participated in the formation of inclusions, consuming harmful elements such as As and P, and also promoted the heterogeneous nucleation of the graphite and segregated, in the form of solute atoms, at its interfaces. Full article

Lacunary polyoxometalates (LPOMs) are key precursors for the synthesis of functional POMs. To date, reviews dedicated to behavioral studies of LPOMs often comprise the role of metal ions, including transition metal (TM) and rare earth (RE) ions, in extending and stability of high-nuclearity clusters. In contrast, the role of organic ligands in the structures and properties of lacunary-based hybrids has remained less explored. In this review, we focus on the role of organic fragments in the self-assembling process of POM-based architectures and discuss relationships between the nature and structure of organic ligand and properties such as the topology of hybrid inorganic–organic material in RE and TM-RE heterometallic derivatives of lacunary Keggin-type POMs. The effects of organic fragment in mixed ligand hybrids are also briefly reviewed. Full article

Moss biomonitoring technique was used for a heavy-metal pollution study in Macedonia in the framework of the International Cooperative Program on Effects of Air Pollution on Natural Vegetation and Crops (UNECE IPC Vegetation). Moss samples (n = 72) were collected during the summers of 2002, 2005, and 2010. The contents of 41 elements were determined by neutron activation analysis, atomic absorption spectrometry, and inductively coupled plasma atomic emission spectrometry. Using factor and cluster analyses, three geogenic factors were determined (Factor 1, including Al, As, Co, Cs, Fe, Hf, Na, Rb, Sc, Ta, Th, Ti, U, V, Zr, and rare-earth elements–RE; Factor 4 with Ba, K, and Sr; and Factor 5 with Br and I), one anthropogenic factor (Factor 2, including Cd, Pb, Sb, and Zn), and one geogenic-anthropogenic factor (Factor 3, including Cr and Ni). The highest anthropogenic impact of heavy metal to the air pollution in the country was from the ferronickel smelter near Kavadraci (Ni and Cr), the lead and zinc mines in the vicinity of Makedonska Kamenica, Probištip, and Kriva Palanka in the eastern part of the country (Cd, Pb, and Zn), and the former lead and zinc smelter plant in Veles. Beside the anthropogenic influences, the lithology and the composition of the soil also play an important role in the distribution of the elements. Full article

Combining the sol-gel method for fiber material production with the granulated silica method for preform assembly results in a robust method that offers a high degree of freedom regarding both the composition and the geometry of the produced fiber. Using this method, two types of Yb-doped silica glass composition, that feature an excess in P concentration with respect to Al, have been prepared. The elemental distributions in a fiber core were analyzed by scanning transmission electron microscopy (STEM). The elemental mapping shows a similar localization of Al, P and Yb through the microstructure. In addition, the influence of the variation in the co-dopant concentration, with respect to Yb, on the fiber properties has been investigated. The results show an increase in the refractive index step and in the fiber’s transmission loss as the excess concentration of P increases. A significant contribution to the losses can be assigned to the existence of impurities such as iron, which was detected in our samples by mass spectrometer. Single exponential fluorescence decays with lifetimes of around 0.88 ms were measured for the two compositions. Finally, pumping at 976 nm a laser slope efficiency of 67% at 1031 nm was achieved for one of the fiber compositions. Full article

Effects of substitutions of rare earth (RE) elements (Y, La, Ce, and Nd) to the Zr-based AB₂ multi-phase metal hydride (MH) alloys on the structure, gaseous phase hydrogen storage (H-storage), and electrochemical properties were studied and compared. Solubilities of the RE atoms in the main Laves phases (C14 and C15) are very low, and therefore the main contributions of the RE additives are through the formation of the RENi phase and change in TiNi phase abundance. Both the RENi and TiNi phases are found to facilitate the bulk diffusion of hydrogen but impede the surface reaction. The former is very effective in improving the activation behaviors. −40 °C performances of the Ce-doped alloys are slightly better than the Nd-doped alloys but not as good as those of the La-doped alloys, which gained the improvement through a different mechanism. While the improvement in ultra-low-temperature performance of the Ce-containing alloys can be associated with a larger amount of metallic Ni-clusters embedded in the surface oxide, the improvement in the La-containing alloys originates from the clean alloy/oxide interface as shown in an earlier transmission electron microscopy study. Overall, the substitution of 1 at% Ce to partially replace Zr gives the best electrochemical performances (capacity, rate, and activation) and is recommended for all the AB₂ MH alloys for electrochemical applications. Full article