RE Metals Research Articles

Frustrated Lewis Pair-Type Reactivity of Intermolecular Rare-Earth Aryloxide and N-Heterocyclic Carbene/Olefin Combinations.

This work reports the cooperative reactivity of rare-earth aryloxide complexes with N-heterocyclic carbene (NHC) or N-heterocyclic olefin (NHO), showcasing their synergistic effect on the activation of H2 and diverse organic substrates. Reactions of RE(OAr)3 (RE=La, Sm, and Y; Ar=2,6-tBu2-C6H3) with unsaturated NHC ItBu (:C[N(R)CH]2, R=tBu) isolated abnormally bound RE metal NHC complexes RE/aNHC. In contrast, no metal-NHO adducts were formed when RE(OAr)3 were treated with NHO (R2C=C[N(R)C(R)]2, R=CH3). Both RE/aNHC and RE/NHO Lewis pairs enabled cooperative H2 activation. Furthermore, RE(OAr)3 were found to catalyze the hydrogenation of the exocyclic C=C double bond of NHO under mild conditions. Moreover, treatment of the La/aNHC complex with benzaldehyde produced a La/C4 1,2-addition product. The La/NHO Lewis pair could react with (trimethylsilyl)diazomethane and α, β-conjugated imine, affording an isocyanotrimethylsilyl lanthanum amide complex and a La/C 1,4-addition product, respectively.

Fluoride-treated rare earth-free magnesium alloy ZK30: An inert and bioresorbable material for bone fracture treatment devices.

Bone fractures represent a common health problem, particularly in an increasingly aging population. Bioresorbable magnesium (Mg) alloy-based implants offer promising alternatives to traditional metallic implants for the treatment of bone fractures because they eliminate the need for implant removal after healing. The Mg-Y-rare-earth (RE)-Zr alloy WE43, designed for orthopedic implants, has received European Conformity mark approval. However, currently, WE43 is not clinically used in certain countries possibly because of concerns related to RE metals. In this study, we investigated the use of a RE-free alloy, namely, Mg-Zn-Zr alloy (ZK30), as an implant for bone fractures. Hydrofluoric acid (HF) treatment was performed to improve the corrosion resistance of ZK30. HF-treated ZK30 (HF-ZK30) exhibited lower corrosion rate and higher biocompatibility than those of WE43 in in vitro experiments. After implanting a rod of HF-ZK30 into the fractured femoral bones of mice, HF-ZK30 held the bones and healed the fracture without deformation. Treatment results of HF-ZK30 were comparable to those of WE43, indicating the potential of HF-ZK30 as a bioresorbable and safe implant for bone repair.

Rare earth removal from pyroprocessing fuel product for preparing MSR fuel

A series of experiments were performed to produce a fuel source for a molten salt reactor (MSR) through pyroprocessing technology. A simulated LiCl–KCl–UCl3-NdCl3 salt system was prepared, and the U element was fully recovered using a liquid cadmium cathode (LCC) by applying a constant current. As a result, the salt was purified with an UCl3 concentration lower than 100 ppm. Subsequently, the U/RE ingot was prepared by melting U and RE metals in Y2O3 crucible at 1473 K as a surrogate for RE-rich ingot product from pyroprocessing. The produced ingot was sliced and used as a working electrode in LiCl–KCl–LaCl3 salt. Only RE elements were then anodically dissolved by applying potential at −1.7 V versus Ag/AgCl reference electrode. The RE-removed ingot product was used to produce UCl3 via the reaction with NH4Cl in a sealed reactor.

Universal and Energy-Efficient Approach to Synthesize Pt-Rare Earth Metal Alloys for Proton Exchange Membrane Fuel Cell.

Traditional synthesis methods of platinum-rare earth metal (Pt-RE) alloys usually involve harsh conditions and high energy consumption because of the low standard reduction potentials and high oxophilicity of RE metals. In this work, a one-step strategy is developed by rapid Joule thermal-shock (RJTS) to synthesize Pt-RE alloys within tens of seconds. The method can not only realize the regulation of alloy size, but also a universal method for the preparation of a family of Pt-RE alloys (RE=Ce, La, Gd, Sm, Tb, Y). In addition, the energy consumption of the Pt-RE alloy preparation is only 0.052kWh, which is 2-3 orders of magnitude lower than other reported methods. This method allows individual Pt-RE alloy to be embedded in the carbon substrate, endowing the alloy catalyst excellent durability for oxygen reduction reaction (ORR). The performance of alloy catalyst shows negligible decay after 20k accelerated durability testing (ADT) cycles. This strategy offers a new route to synthesize noble/non-noble metal alloys with diversified applications besides ORR.

Influence of rare earth metals on inclusion modification of dual phase steel

ABSTRACT Inclusions are very critical in advanced high-strength steels as they are used in automobile and aerospace industries in which modification of inclusions is required. In this investigation, Rare Earth Metals (REM) have been used to control and modify the inclusions in the steel. With the addition of REMs, the total sulphur content present in the steel has been reduced by 22%. An inclusion study has been performed using the inclusion classifier and ISO-4967 method. Total inclusions and the number of inclusions at higher indexes (severity) are reduced by adding REM. The chemistry of the modified inclusions, such as oxides, sulphides and oxysulphides of REM, is compatible with the steel matrix and does not have harmful effects. With the addition of REM, the global cleanliness index value at 1.5, 2, 2.5 and 3 indexes are decreased. This may be attributed to the REM breaking down the stringers. Whereas value has been increased at 0.5 and 1 indexes after the addition of RE metals, inclusions sizes are reduced, which is not harmful to the properties of the steel.

Managing the micro-structure and properties of Sm-ZnO thin films by tuning the contents of Sm

The microstructural variations in zinc oxide (ZnO) nanostructures are probed caused by the incorporation of RE metal ion Sm3+ in replacement of Zn2+. Sm-doped ZnO nanostructures with Sm concentration of 6–10 wt % is synthesized via a simple sol gel-dip coating synthetic technique. The current research looks into the physical, surface morphology, dielectric, optical, and magnetic properties of Samarium doped ZnO nanostructures. Structural and morphological investigations are primarily carried out using XRD and SEM techniques. The data from XRD identified the synthesized Sm doped ZnO nanostructures crystallize in a wurtzite hexagonal structure. The Sm dopant is incorporated into the Zn matrix. After adding Sm in ZnO, a slight variation in crystallite size is noticed. The estimates of the optical energy band gap based on optical transmittance measurements show that the band gap is widened. The variation in dielectric properties of Sm-ZnO is assumed to be the result of the increase in Sm doping %. The various functional groups that appeared in the prepared nanostructures are identified using FTIR. These prepared nanostructures are highly recommended for sensing applications as well as for optoelectronic devices.

Nickel-rare earth (Ce, Sm, Dy) alloy electrodes for hydrogen peroxide reduction in direct liquid fuel cells

• Nickel-rare earth (Ce, Sm, Dy) alloys (5 and 10 at.% RE) were prepared by arc melting. • Alloys structure, morphology, and composition were characterized by SEM/EDXS and XRPD. • LSV and CA evaluated Ni-RE alloys’ activity for hydrogen peroxide reduction reaction. • HPRR in alkaline media proceeds with 1.7 electrons exchanged at Ni 0.95 Ce 0.05 electrode. • Good performance of Ni 0.95 Ce 0.05 alloy suggests application in direct liquid fuel cells. Hydrogen peroxide (H 2 O 2 ), a reactive oxygen species, is an excellent alternative to oxygen as an oxidant for direct liquid fuel cells (DLFCs). To overcome problems related to scarcity and high cost of commonly used noble metal electrodes, nickel (Ni) and nickel-rare earth (RE = Ce, Sm, Dy) alloys are synthesised and evaluated as electrode materials for H 2 O 2 reduction reaction (HPRR) in alkaline media. These Ni-RE alloys (containing 5 and 10 at.% RE metal) are produced by arc melting and analysed by X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Voltammetric and chronoamperometric measurements are employed to assess the performance of the Ni-RE alloys for HPRR in 2 M NaOH solution. The Ni 0.95 Ce 0.05 alloy exhibits impressively high catalytic activity for HPRR, with a number of exchanged electrons of 1.7 and activation energy of 38 kJ mol -1 , suggesting its application as cathode material in DLFCs.

Dramatic Enhancement of Rare-Earth Metal–Organic Framework Stability Via Metal Cluster Fluorination

Rare-earth polynuclear metal–organic frameworks (RE-MOFs) have demonstrated high durability for caustic acid gas adsorption and separation based on gas adsorption to the metal clusters. The metal clusters in the RE-MOFs traditionally contain RE metals bound by μ3–OH groups connected via organic linkers. Recent studies have suggested that these hydroxyl groups could be replaced by fluorine atoms during synthesis that includes a fluorine-containing modulator. Here, a combined modeling and experimental study was undertaken to elucidate the role of metal cluster fluorination on the thermodynamic stability, structure, and gas adsorption properties of RE-MOFs. Through systematic density-functional theory calculations, fluorinated clusters were found to be thermodynamically more stable than hydroxylated clusters by up to 8–16 kJ/mol per atom for 100% fluorination. The extent of fluorination in the metal clusters was validated through a 19F NMR characterization of 2,5-dihydroxyterepthalic acid (Y-DOBDC) MOF synthesized with a fluorine-containing modulator. 19F magic-angle spinning NMR identified two primary peaks in the isotropic chemical shift (δiso) spectra located at −64.2 and −69.6 ppm, matching calculated 19F NMR δiso peaks at −63.0 and −70.0 ppm for fluorinated systems. Calculations also indicate that fluorination of the Y-DOBDC MOF had negligible effects on the acid gas (SO2, NO2, H2O) binding energies, which decreased by only ∼4 kJ/mol for the 100% fluorinated structure relative to the hydroxylated structure. Additionally, fluorination did not change the relative gas binding strengths (SO2 > H2O > NO2). Therefore, for the first time the presence of fluorine in the metal clusters was found to significantly stabilize RE-MOFs without changing their acid-gas adsorption properties.

Enhanced visible light activated mesoporous titania by rare earth metal doping

The photocalalytic activity of four mesoporous RE metal (Ce3+, La3+, Sm3+, Dy3+) doped titania was compared and investigated under UVA and visible light irradiation. The photocatalysts were synthesized by using a template guided sol-gel method and were fully characterized by XRD, FTIR, UV–Vis, TEM and Nitrogen adsorption-desorption techniques. The presence of the dopant in the mesoporous RE metal doped titania samples has been demonstrated by FTIR, XPS and EDX techniques. The results confirm that the doping of titania particles with rare earth metals could be achieved and the doping process do not change the crystalline phase of TiO2. The photocatalytic activity decreases in the following order: Sm-TiO2>Dy-TiO2>La–TiO2>Ce–TiO2. Moreover, quenching experiments were carried out to further disclose the contribution of involved ROS in the process.

A Series of Rare-Earth Mesoionic Carbene Complexes.

We report the synthesis and characterisation of a series of rare-earth mesoionic carbene complexes, [RE{N(SiMe3 )2 }3 {CN(Me)C(Me)N(Me)CH}] (3RE, RE=Sc, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), greatly expanding the limited library of f-block mesoionic carbene complexes. These complexes were prepared by treatment of the parent RE-triamides with an N-heterocyclic olefin (NHO), where an NHO backbone proton undergoes a formal 1,4-proton migration to the NHO-methylene group. For all RE(III) metals, as expected, quantum chemical calculations suggest only a σ-component to the metal-carbene bonding, in contrast to a previously reported uranium(III) congener where the 5f3 metal engages in a weak π-back-bond to the MIC. All complexes were characterised by static variable-temperature magnetic measurements, and dynamic magnetic measurements reveal that 3Dy and 3Er are field-induced single-molecule magnets (SMMs), with Ueff energy barriers of 35 and 128 K, respectively. Complex 3Dy is, as expected, a poorly performing SMM, but conversely 3Er performs unexpectedly well.

Magnetic Properties of Tetragonal SmFe12−xMox Alloys in Bulk and Melt‐Spun Ribbons

Currently, electric motors and generators use high‐energy permanent magnets based on RE2Fe14B phases (RE: rare earth) with high amounts of RE often including heavy‐RE metals (Dy, Tb), the most critical group of the raw materials. REFe12 alloys are seen as potential alternatives to RE2Fe14B because they contain a significantly lower amount of RE metals with similar or better values of remanent magnetization (MR) and high magnetocrystalline anisotropy, which can give rise to a large energy product (BH)max. Herein, the effect of heat treatments on the coercivity and magnetic properties on melt‐spun ribbons of SmFe12−xMox (x = 0.5, 1) alloys with wheel speeds of 15 and 35 m s−1 is studied. The maximum coercivity after heat treatments is obtained in as‐spun ribbons at a speed of 35 m s−1. For the x = 0.5 ribbons, μ0Hc increases from 0.06 to 0.36 T, while for the x = 1.0 ones μ0Hc is enhanced from 0.02 to 0.34 T. The highest values of saturation magnetization are obtained for the x = 0.5 ribbons (≈145 Am2 kg−1).

Electrochemical Deposition of U and RE Elements Using the Stirred Liquid Cadmium Cathode in LiCl-KCl Molten Salts

This study was conducted in an attempt to understand the effect of a stirred liquid cadmium cathode (LCC) on the electrodeposition of U and U/RE on Cd. For this purpose, a series of electrowinning tests were performed using an LCC equipped with a Cd stirrer. Initially, three runs of the U electrodeposition tests were conducted using LiCl-KCl-UCl3 at 500°C under a constant current. From the results obtained from the initial three runs, it was found that the maximum deposited amount of U was 7.4 wt% U/Cd. U dendrite formation on the LCC crucible was not observed across each of the three runs. Three additional runs were conducted using LiCl-KCl-UCl3-RECl3 to determine the extent of U/RE electrodeposition. The maximum number of moles of U + RE metals deposited was 0.07, a value estimated to be 2.14 times higher than the solubility limits exhibited by these metals in Cd. The results of this study show that the use of a Cd stirrer significantly improves the extent of U deposition.

Mechanistic Insights into the Synthesis of Platinum–Rare Earth Metal Nanoalloys by a Solid-State Chemical Route

Platinum–rare earth metal (Pt–RE) nanoalloys are among the most active electrocatalysts for the oxygen reduction reaction and are predicted to exhibit long-term stability in proton-exchange membrane fuel cells. We have recently developed a solid-state chemical route for synthesizing this family of alloy materials, which is carried out under seemingly impossible conditions. Here, we report an in-depth understanding of the synthesis mechanism, obtained through systematic investigations of the chemical processes involved at different stages of the synthesis process and the structural evolution of the intermediate products. The formation of Pt–RE nanoalloys is made possible by a series of consecutive chemical and physical processes, including the polymerization processes of the nitrogen-rich precursor, the formation of a porous RE carbodiimide phase, the mobility of the formed metal phases on the carbon support, the reduction of the RE metals driven by the alloying reaction, and so forth. This thorough understanding of the mechanism of the synthesis process lays the foundation for optimizing the synthesis procedures and maneuvering this method to synthesize Pt–RE alloy materials with the desired structures and properties.

Effect of rare earth elements on coatings developed by thermal spraying processes (TSP) – A brief review

A coating is deployed on the substrate by different deposition techniques to elevate the substrate's surface properties, such as chemical, mechanical, and tribological. The elevation in the properties of the substrate depends on elements used in coating powder. In this work, the effect and significance of rare earth elements on the substrate has been presented. The objective of the work is coating by different thermal spraying methods. From the literature survey on TSP, there is a significant increase in corrosion resistance than other material properties. The tribological properties of substrate material were analysed with and without the rare earth material in coating powder by various researcher’s work. It is found that very less or little researchers have explored rare earth material as a coating material. There are different areas in which these coatings are used for various applications like the turbine's blade, aero-engines, miniaturized electronics, display panels, and others. By using RE metals mechanical, physical, tribological, and thermal shock resistance of the substrate material increased considerably.

Effect of Rare Earth Metal (RE = La, Pr, Nd, Y) Doping on Co–Ce Composite Oxide and Its Application in Catalytic Combustion of Chlorobenzene

Rare earth metal (RE = La, Pr, Nd, Y)-doped CoCeOx catalysts were prepared and evaluated for eliminating chlorobenzene (CB). Characterization results showed that the doped RE metal simultaneously a...

Implementation of ZnSnO3 nanosheets and their RE (Er, Eu, and Pr) materials: Enhanced photocatalytic activity

ZnSnO3, ZnSnO3@Er, ZnSnO3@Eu, and ZnSnO3@Pr materials were synthesized by a hydrothermal method, these active materials characterized by XRD, Raman, DRS-UV, FT-IR, BET surface areas and Scanning electron microscopy studies. The ZnSnO3 nanosheets meta-stable form was confirmed by XRD. Here, addressing to the pure and doped materials functional groups were evaluated by FT-IR spectroscopy. ZnSnO3, ZnSnO3@Er, ZnSnO3@Eu, and ZnSnO3@Pr rotational vibrations frequency modes were predicted by the Raman spectroscopy. Our results are marvelously, the obtained bandgap energies at 3.5 eV for pure sample and ZnSnO3@Er, ZnSnO3@Eu and ZnSnO3@Pr energies at 3.06 eV, 3.04 eV and 3.02 eV. The synthesized pure samples get a sheet-like morphology and doped for RE metals than morphology was changing for nanocubes. We assess for all samples that were focused on photocatalytic dye degradation for Methylene blue dye; hence, we are discussing these approaches, ZnSnO3@Pr/Methylene blue sample was a great improvement and high decolorization efficiency compared with ZnSnO3@Er, ZnSnO3@Eu nanocubes. The ZnSnO3@Pr sample surface area was investigated by BET analysis. In addition, we are testing the phenol degradation with wastewater. The ZnSnO3@Er, ZnSnO3@Eu catalysts were determined to the less efficiency when comparing to the ZnSnO3@Pr material. The ZnSnO3@Pr material results have more efficiency and a very good recyclable stability nature.

Synthesis of Pt-Rare Earth Metal Nanoalloys.

Chemical synthesis of platinum-rare earth metal (Pt-RE) nanoalloys, one of the most active catalysts for the oxygen reduction reaction, has been a formidable challenge, mainly due to the vastly different standard reduction potentials of the two metals and high oxophilicity of the latter. Here we report a universal chemical process to prepare Pt-RE nanoalloys with tunable compositions and particle sizes. Pt and RE metal ions from the most common hydrated metal salts are first atomically embedded into an in situ formed C-N network, yielding a stable compound insensitive to O2 and H2O. The Pt-RE nanoalloys are subsequently obtained by heating the compound under a mild reducing atmosphere (e.g., 3.3% H2/Ar). The key intermediate step of the process is the formation of RE carbodiimides (RE2(CN2)3) along with Pt particles. This synthesis mechanism suggests an efficient strategy to prepare nanoalloys with highly reactive metals.

Preparations, optical, structural, conductive and magnetic evaluations of RE's (Pr, Y, Gd, Ho, Yb) doped spinel nanoferrites

Rare earths RE's (Pr, Y, Gd, Ho, Yb) substituted MnZn spinel ferrites with composition of Mn0.5Zn0.5M0.02Fe1.98O4 (M = Pr, Y, Gd, Ho, Yb) are prepared by sol gel combustion approach. Low sintering temperature (500 °C) is used to sinter the RE's doped MnZn samples. MnZn samples are further characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to measure the cubic crystalline structure, particle size, morphology, porosity and grain size. Cubic crystalline phase of prepared RE's doped MnZn ferrites is confirmed by x-ray diffraction (XRD). The morphology, porosity and grain size are observed using FESEM. The magnetic properties of RE's doped MnZn nanoferrites are analyzed by vibrating sample magnetometer (VSM). Coercivity (Hc), remanence (Mr) and saturation magnetization (Ms) are calculated from the magnetic loops. The saturation and remanence of the nanoferrites are increased by the substitution of RE's metal ions and varies from 14.76 to 26.36 emu/g and 9.98–22.48 emu/g respectively. Bohr magneton and anisotropy constant are calculated from the recorded magnetic data. The conductive analysis of the prepared samples is studied at 40 °C −300 °C temperature, leading to the conductivity measurements from 1.12 × 10-2 Ω-1-cm-1 to 9.52 × 10-2 Ω-1-cm-1. UV–Vis spectroscopy is used to determine the semi conducting nature of RE's doped MnZn spinel ferrite samples. The magnetic, conductive and optical study of the RE's doped MnZn nanoferrites sintered at low temperature suggests the use of these materials for microwave absorption, supercapacitor, lithium ion batteries and nanoelectronics industrial applications.

Rational Design and Synthesis of Hexanuclear Rare Earth the-a Metal–Organic Frameworks Platform Based on RE6O4(OH)4(COO)8 Clusters

A series of hexanuclear RE(III) metal–organic frameworks, UPC-68, with the-a topology, have been successfully designed and synthesized by topology guidance (RE = rare earths). It is worth mentioning that the synthetic RE(III)-MOFs are constructed by a stable D4h 8-connected RE6 cluster, which is reported first, and a D3h 3-connected ligand (H3CTTA). The results indicate that UPC-68-Tb shows the characteristic recognition of 4-nitroaniline (4-NA), 2-nitroaniline (2-NA), and 4-nitrophenol (4-NP), and iodine adsorption capacity.

Enhanced catalytic properties of rare-earth substituted cobalt ferrites fabricated by sol-gel auto-combustion route

Abstract Cobalt ferrite has been extensively used in catalysis owing to their remarkable physical and chemical properties. Additionally, further modifications in these properties can be achieved by changing cation distribution. The ionic radii of rare earth (RE3+) ions are larger than the Fe3+ ions. So, on the replacement of Fe3+ ion in cobalt ferrite with even a small amount of RE3+ ion, the physical and chemical properties get greatly affected due to structural distortion and lattice strain. So, in the present work doping of RE element into ferrite crystal lattice has been done via sol-gel auto-combustion route. The synthesized samples were well characterized using various techniques and the change in their structural, magnetic and optical properties was investigated. Further, for studying the effect of RE metal ion substitution on the catalytic properties, the samples were exploited as photo-Fenton catalysts for the removal of cationic and anionic dyes. The RE substituted cobalt ferrite samples exhibited remarkable enhancement in the catalytic activity in comparison to pure cobalt ferrite. The synthesized samples thus can be potentially used for combating the environmental properties.