Rare Earth Research Articles

Research progress on microbial adsorption of radioactive nuclides in deep geological environments.

Due to the development and utilization of nuclear energy, the safe disposal of nuclear waste needs to be urgently addressed. In recent years, the utilization of microorganisms' adsorption capacity to dispose of radioactive waste has received increasing attention. When compared with conventional disposal methods, microbial adsorption exhibits the characteristics of high efficiency, low cost, and no secondary pollution. In the long term, microbial biomass shows significant promise as specific chemical-binding agents. Optimization of biosorption conditions, identification of rare earth element binding sites, and studies on the sorption capacities of immobilized cells provide compelling reasons to consider biosorption for industrial applications in heavy metal removal from solutions. However, the interaction mechanism between microorganisms and radioactive nuclides is very complex. This mini-review briefly provides an overview of the preparation methods, factors affecting the adsorption capacity, and the mechanisms of microbial adsorbents.

Characterization of NiCuOxNy Coatings Obtained via RF Sputtering: Structure, Morphology, and Optical Properties.

The rapid advancement of technology necessitates the continual development of versatile materials that can adapt to new electronic devices. Rare earth elements, which are scarce in nature, possess the set of properties required for use as semiconductors. Consequently, this research aims to achieve similar properties using materials that are abundant in nature and have a low commercial cost. To this end, nickel and copper were utilized to synthesize thin films of nickel-copper binary oxynitride via reactive RF sputtering. The influence of nitrogen flow on the structure, morphology, chemical composition, and optical properties of the films was investigated using various characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS), as well as transmittance and absorbance measurements. The crystalline structure of the films shows that they can have preferential growth or be polycrystalline according to the nitrogen flow used during deposition and that both the oxides and oxynitrides of metals are formed. We identified unknown phases specific to this material, termed "NiCuOxNy". The morphology revealed that the grain size of the coatings was dependent on the nitrogen flow rate, with grain size decreasing as the nitrogen flow rate increased. Notably, the coatings demonstrated transparency for wavelengths exceeding 1000 nm, with an optical band gap ranging from 1.21 to 1.86 eV.

Emerging magnetic materials for electric vehicle drive motors

AbstractIncreasing demand for electric vehicles (EVs) is increasing demand for the permanent magnets that drive their motors, as approximately 80% of modern EV drivetrains rely on high-performance permanent magnets to convert electricity into torque. In turn, these high-performance permanent magnets rely on rare earth elements for their magnetic properties. These elements are “critical” (i.e., at risk of limiting the growth of renewable energy technologies such as EVs), which motivates an exploration for alternative materials. In this article, we overview the relevant fundamentals of permanent magnets, describe commercialized and emerging materials, and add perspective on future areas of research. Currently, the leading magnetic material for EV motors is Nd2Fe14B, with samarium-cobalt compounds (SmCo5 and Sm2Co17) providing the only high-performing commercialized alternative. Emerging materials that address criticality concerns include Sm2Fe17N3, Fe16N2, and the L10 structure of FeNi, which use lower cost elements that produce similar magnetic properties. However, these temperature-sensitive materials are incompatible with current metallurgical processing techniques. We provide perspective on how advances in low-temperature synthesis and processing science could unlock new classes of high-performing magnetic materials for a paradigm shift beyond rare earth-based magnets. In doing so, we explore the question: What magnetic materials will drive future EVs? Graphical abstract

Variations in pore structures and permeabilities of ion adsorption rare earth ores during simulated in-situ leaching: Effect of newly formed clay particles and their swelling

In-situ leaching is essential for mining rare earth elements (REEs) from ion-adsorption rare earth (RE) ores. The efficiency of RE mining is dependent on the permeabilities of ion-adsorption RE ores, and the permeabilities are controlled by their pore structures. However, the current understanding of the pore structures and permeabilities of the RE ores during leaching is limited, particularly their dynamic variations, the controlling roles of different pore structure parameters on the permeability, the roles of the influencing factors and the mechanisms causing the variations. To investigate the above-mentioned issues, we conducted an experimental study of simulated in-situ leaching on undisturbed ion-adsorption RE ore samples under different conditions via constant waterhead permeability tests. The leaching conditions included leaching time, concentration and waterhead of the (NH4)2SO4 solution. Three-dimensional (3-D) pore structures of the RE ores before, during, and after leaching were constructed via X-ray computed tomography, and their pore structure parameters were measured using 3-D image computation. It was observed that the dynamic variations in both the pore structure parameters and permeability coefficients of the RE ores occurred in three distinct stages: rapid reduction, less rapid reduction, and little reduction. The experimental results also revealed that the permeability coefficients of the RE ores were primarily dependent on the average coordination number among the seven pore structure parameters examined, and that the pore throats larger than 30 μm in diameter served as the most effective seepage channels within the RE ores. The waterhead of the leaching solution had a stronger influence on the variations in pore structures and permeabilities compared to that of the concentration. Analysis of the particle/aggregate size distribution and mineralogical compositions of the RE ores before and after leaching indicated that the decreases in the pore structure parameters and permeabilities were largely attributed to clogging of the pore throats and pores by migrated and newly formed clays, as well as swelling of the latter. The newly formed clays were the products of the decomposition of K-feldspar and mica resulting from chemical reactions with the leaching solution. The clays from the two sources occurred in disaggregated and aggregated forms. The results of this study provide an important reference for the mining of RE ores via leaching.

Sodium alginate/polyvinyl alcohol for the recovery of rare earth elements from mining wastewater: Mechanism and properties

With the demand for rare earth elements (REEs) increasing in the high-tech sector, the recovery of REEs from secondary sources is becoming very critical. In this study, sodium alginate/polyvinyl alcohol (SA/PVA) beads obtained by cross-linking alginate with polyvinyl alcohol were used to recover REEs from real rare-earth wastewaters. The results showed that SA/PVA beads are less affected by temperature and exhibited adsorption selectivity for REEs. The efficiency of adsorbing REEs ranged from 27.6% to 52.6%, but was significantly higher than that of 9.2% Mn. Meanwhile, among the observed REEs, SA/PVA beads revealed a preference for light REEs (44.3% − 52.6%). The adsorption process was investigated utilizing advanced characterization methods, namely Scanning Electron Microscope, Fourier Transform Infrared Spectrometer, and X-ray Diffraction Spectra. Combined with the results of Pearson correlation analysis, we proposed that the adsorption process involves the combined effects of ion exchange, complexation, electrostatic interaction and pore filling. As well, a desorption efficiency of more than 76.9% can be achieved with sodium citrate, which makes possible the effective recovery of REEs. In summary, this study provides a promising green, environmentally friendly and sustainable material for the enrichment and recovery of REEs from mining wastewater.

The higher-order moments connectedness between rare earth and clean energy markets and the role of geopolitical risk:New insights from a TVP-VAR framework

Against the backdrop of escalating geopolitical risks, the interdependence between rare earth and clean energy markets are crucial for cross-market investors and regulators. However, previous research has not adequately examined the higher-order moment connections between these markets. This study addresses this gap by integrating GRACHSK and TVP-VAR methods to explore the asymmetric and tail risk connectedness between rare earth and solar, wind, nuclear, and electric vehicle markets. Further, we investigated how geopolitical risks impact these connections over time. The results reveal significant higher-order moment connectedness between the clean energy and rare earth markets, each serving as an exporter and receiver, respectively. Among these, wind energy and solar energy exhibit significant net spillovers of skewness and kurtosis to rare earths. These high-order moment spillovers are time-varying and exacerbate during major geopolitical crises, such as the COVID-19 pandemic and the Russian-Ukraine war. The portfolios with minimum connectedness are effective at hedging extreme risks, particularly in terms of kurtosis. It implies that portfolios constructed based on higher-order moments can better hedge against extreme risks. GPR exacerbates higher-order moment spillovers between rare earth and clean energy markets in the short- and medium-term. In particular, the impulse response of kurtosis spillovers to GPR shocks shows prominent and frequent fluctuations, indicating that extreme risk spillover effects with significant lag effects would rapidly diffuse across various markets when geopolitical risks occur. The research findings contribute to three aspects: First, the connectedness analysis offers a network and dynamic perspective on extreme risk management between rare earth and clean energy markets. Second, higher-order moments can enhance the returns of diversified cross-market investment portfolios. Third, the conclusions aid in understanding the evolving patterns of rare earth and clean energy markets under geopolitical risk events, facilitating timely investment and regulatory strategies.

Interface Modulation of 2D Superlattice Heterostructures with Oxygen-enriched Sites and Dissolution Restraint for Effective Rare-earth Elements Extraction

Effective recovery of rare earth elements from wastewater is crucial for the modern industry, as well as for protecting the human health and ecosystem. Nevertheless, it is still challenging to realize efficient and selective low-concentration rare earth extraction in systems containing high levels competing metal ions. Here, we report on the fabrication of two-dimensional superlattice heterostructures (VOGO-x) through the alternating restacking of VOPO4 nanosheets and GO-PDDA nanosheets via electrostatic self-assembly. The meticulously organized molecular scale of superlattice heterostructures enable the full exposure of accessible adsorption sites and facilitate the transport of rare earth ions, meanwhile the abundant oxygen-containing phosphate groups within the interlayer can realize selective rare earth ions extraction. Furthermore, the tunable interlayer interaction can promote structure stability to prevent dissolution. Consequently, VOGO-11 possesses excellent rare earth adsorption performance, with a saturated adsorption capacity (Nd(III) 631.52 mg/g, Dy(III) 689.48 mg/g, Lu(III) 716.06 mg/g), high utilization rate of adsorption sites and short adsorption equilibrium time of simply 10 min in the REE aqueous solution. Furthermore, VOGO-11 exhibits outstanding selective rare earth adsorption ability over a wide range of metal ions in the low-concentration simulated wastewater and actual leaching tailings. These results demonstrate the material’s promising potential in capturing rare earth ions and pave the way to the development of two-dimensional superlattice heterostructures through interface modulation for effective rare earth extraction.

Rare earth elements as a tool to study the foliar nutrient uptake phenomenon under ambient and elevated atmospheric CO2 concentration

The ability of plants to uptake nutrients from mineral dust lying on their foliage may prove to be an important mechanism by which plants will cope with increasing CO2 levels in the atmosphere. This mechanism had only recently been reported and was shown to compensate for the projected dilution in plants ionome. However, this phenomenon has yet to be thoroughly studied, particularly in terms of the expected trends under different dust types and varying atmospheric CO2 concentrations, as projected by the IPCC. We treated plants grown under ambient (415 ppm) and elevated CO2 (850 ppm) conditions with either desert dust, volcanic ash, and fire ash analogues by applying it solely on plant foliage and studied their Rare Earth Elements concentrations and patterns. The Rare Earth Elements compositions of the treated plants originated from the dust application, and their incorporation into the plants led to a significant increase in plants vitality, evident in increased photosynthetic activity and biomass. Two trends in the foliar nutrient uptake mechanism were revealed by the Rare Earth Elements, one is that different treatments affected the plant in decreasing order volcanic ash > desert dust > fire ash. The second trend is that foliar intake becomes more significant under elevated CO2, an observation not previously seen. This testifies that the use of Rare Earth Elements in the study of foliar nutrient uptake, and other biological mechanisms is fundamental, and that foliar pathways of nutrient uptake will indeed become more dominant with increasing CO2 under expected atmospheric changes.

Preventing emulsification during rare earth solvent extraction by the addition of Span 80 to enhance the interfacial stability of the P507 oil droplets

The demand for rare earth elements is increasing daily with rapid economic development, thereby increasing the requirements for its separation and purification technologies. The major method for purification and separation of rare earth in the industry is currently solvent extraction. In the actual production process, emulsification often occurs because of improper control of the organic phase, aqueous phase properties or operating conditions, and resulting in resource wastage and environmental pollution. This has become an issue that restricts the development of the rare earths industry. To prevent emulsification during rare earth solvent extraction, the organic structure of the P507-kerosene solution was regulated by the addition of Span 80 as a regulator. This study investigated the effects of Span 80 concentration, P507 concentration, saponification degree and the amount of pre-loading rare earth elements in the organic phase after adding Span 80 on the extraction efficiency of Er3+ and oil content in the raffinates. The results demonstrated that when the content of Span 80 was 6 %, the saponification degree of P507 in the organic phase was 10 %, the concentration of Er3+ in the aqueous phase was 0.5 g /L, the pH value in the aqueous phase was 3, the phase ratio (VO: VA) was 1:2, the extraction efficiency could still reach more than 99 %, and the oil content in the raffinates was 13.9 mg/L. The results demonstrated that the final extraction efficiency did not decrease; however, the extraction rate of rare earth elements did. Further, the oil content in the raffinates decreased greatly after the addition of Span 80. The mechanism was investigated using Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The interfacial stability of P507 oil droplets was enhanced by the addition of Span 80. Emulsification was, thus, effectively prevented and the dissolution loss of the organic phase was greatly reduced. The results provide a novel method for preventing emulsification during rare earth extraction at the source, and a novel idea for preventing resource loss and protecting the ecological environment.

Rare earth induced lattice distortion of Bi2WO6 to effectively improve photocatalytic performance: experimental and DFT calculations

The excellent visible light photocatalytic activity of bismuth-based photocatalysts has attracted the interest of many scholars at home and abroad. In this paper, rare earth (Sm, La, Ce, Eu) doped Bi2WO6 photocatalysts were prepared by a one-step hydrothermal method using bismuth nitrate and sodium tungstate as precursors. The microstructures and spectroscopic performances of prepared materials were investigated utilizing characterization methods, such as XRD, XPS, UV-vis, TEM, and N2 adsorption-desorption, etc., and the effluent removal performances were studied by using rhodamine B as a simulated degradation dye and the photodegradation mechanism was investigated in combination with DFT calculations. XRD indicates that the rare earth doping leads to the lattice distortion of the (131) crystal surface of Bi2WO6, and the relative amount of distortion is directly proportional to the photocatalytic activity; UV-vis spectra show that the absorption edge of Bi2WO6 is obviously red-shifted with the rare earth doping, and N2 adsorption-desorption curve show that the doped rare earths make the specific surface area of the sample effectively increased. Moreover, XPS spectrum suggest that the doped rare earth Ce and Eu often exist in the form of metastable oxidation states, and the transformation between Ce3+/Ce4+ and Eu2+/Eu3+ oxidation states is easy to form impurity energy levels between Bi2WO6, which make the energy level significantly enriched to broaden the absorption range and reduce band gap width of the material. DFT calculations further indicate that the rare earths successfully replace Bi sites. One of the main reasons for the improvement of photocatalytic activity is that rare earth doping is easier to replace Bi sites, leading to increased relative aberration; another one is that the arrangement of EVB and ECB in the photocatalytic mechanism is type-II, which contributes to red-shift of absorption edge and effective separation of electron-hole pairs in the photocatalytic process, thus improving the photocatalytic activity.

Preventing emulsification during rare earths solvent extraction by the addition of Span 80 to enhance the interfacial stability of the P507 oil droplets

The demand for rare earth elements is increasing daily with rapid economic development, thereby increasing the requirements for its separation and purification technologies. The major method for purification and separation of rare earth elements in the industry is currently solvent extraction. In the actual production process, emulsification often occurs because of improper control of the organic phase, aqueous phase properties or operating conditions, and resulting in resource wastage and environmental pollution. This has become an issue that restricts the development of the rare earths industry. To prevent emulsification during rare earths solvent extraction, the organic structure of the P507-kerosene solution was regulated by the addition of Span 80 as a regulator. This study investigated the effects of Span 80 content, P507 concentration, saponification degree and the amount of pre-loading rare earth elements in the organic phase after adding Span 80 on the extraction efficiency of Er3+ and oil content in the raffinates. The results demonstrated that when the content of Span 80 was 6 %, the saponification degree of P507 in the organic phase was 10 %, the concentration of Er3+ in the aqueous phase was 0.5 g /L, the pH value in the aqueous phase was 3, the phase ratio (VO: VA) was 1:2, the extraction efficiency could still reach more than 99 %, and the oil content in the raffinates was 13.9 mg/L. The results demonstrated that the final extraction efficiency did not decrease; however, the extraction rate of rare earth elements did. Further, the oil content in the raffinates decreased greatly after the addition of Span 80. The mechanism was investigated using Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The interfacial stability of P507 oil droplets was enhanced by the addition of Span 80. Emulsification was, thus, effectively prevented and the dissolution loss of the organic phase was greatly reduced. The results provide a novel method for preventing emulsification during rare earths extraction at the source, and a novel idea for preventing resource loss and protecting the ecological environment.

Optimization of rare earth magnet recovery processes using oxalic acid in precipitation stripping: Insights from experimental investigation and statistical analysis

Recycling the valuable metals found in spent permanent magnets (REPMs) poses a significant global challenge for the future. This study examines the efficiency of back extraction of rare earth elements (REEs) by oxalic acid solution from di-(2-ethylhexyl) phosphoric acid (D2EHPA) in recycling REPMs. To evaluate the efficiency of this process, several experiments were carried out using designed BOX-Behnken methodology to investigate the effects of various operational and chemical parameters, including stripping solution to loaded organic phase volume ratio (in the range of 1.0–2.0), oxalic acid concentration (ranging from 0.25 to 0.75 M), the stirring rate (ranged between 150 and 350 rpm), and stripping time (ranging from 15 to 45 min) on the REEs recovery and the purity of final production. Analysis of variance was applied to rigorously examine the results statistically. The results showed that more than 85 % of light and 80 % of heavy REEs can be recovered under optimal conditions. Moreover, the final product contained 43.5 % REEs and approximately 0.1 % iron. The stripping experiment using phosphoric acid as the reagent demonstrated ∼57 % light and ∼4 % heavy REEs recovery. Additionally, the recyclability of the organic phase showed its effective reuse for up to four cycles. This study underscores significant progress in the selective recovery of rare earth elements through a relatively straightforward process consuming mild reagents.

Synergetic recycling of permanent magnet and Li-ion battery cathode material for metals recovery

Rare earth element (REE)-based (NdFeB) magnets and lithium−ion batteries (LIBs) are critical for a low−carbon economy. Their production depends on critical elements like REEs, Li, Co and Ni. Recycling of these products have been explored separately as a potential solution. Conventional methods for NdFeB magnets and LIBs face challenges like high energy consumption, lengthy processing, excessive reagent usage, and waste generation. In this study, a novel synergetic recycling methodology is proposed to minimize these challenges. The idea is based on using waste ferrous sulfate solution generated during magnet leaching as a reducing and leaching reagent for battery recycling thereby eliminating the need for additional reagents for oxidation of iron in NdFeB and reduction of cathode material in LIBs. The magnet is leached in diluted H2SO4 at 70 °C followed by double sulfate precipitation for REEs with Na2SO4. The REE-depleted but highly acidic ferrous solution is then used for reductive leaching of cathode material at 90 °C. The overall recovery rates of REEs, Li, Co, Ni, and Mn in this process are >95%. The iron from magnet material is recovered as crystalline and easily-filterable high-grade goethite that can be used as a byproduct. This synergetic approach not only reduces reagent consumption and waste generation aligning with the principles of circular economy but also offers improved efficiency, resource conservation, and environmental sustainability.

Effects of Ce addition on inclusion modification in martensitic stainless steel

The control of inclusion features, i.e., chemical composition, distribution, quantity, and size, is in high demand for stainless steels to achieve good surface quality, pitting corrosion resistance, and mechanical properties. In this paper, the effects of rare earth (RE) modification on the inclusions of martensitic stainless steel were explored. Martensitic stainless steels with various contents of Ce were prepared, and the inclusions in the cast billets were characterized by field emission scanning electron microscopy (FE-SEM) and an automatic analysis system for nonmetallic inclusions in steels (OTS). The effect of Ce on the modification of nonmetallic inclusions during solidification was explored with thermodynamic calculations. The results showed that the addition of Ce modified the oxygen and sulfur inclusions by transforming them from irregular elongated inclusions to nearly spherical RE composite inclusions. Compared with those in basic martensitic stainless steel, nine types of RE inclusions were found in the presence of Ce. As the Ce content increased from 0.048 wt% to 0.092 wt%, the CeAlO3 content decreased, whereas the Ce2O2S content increased. Moreover, there were 80% fewer inclusions than in the basic martensitic stainless steel.

Mineralogical Characteristics of Color-Changing Garnet and the Effect of Light Path Length on Color

The color-changing garnet displays the “alexandrite effect”, changing from green in daylight to purplish-red under incandescent light. The mineralogical characteristics of color-changing garnet is analyzed using Raman spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, an electron probe, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The color of garnets with different thicknesses was calculated using the International Commission on Illumination (CIE 1976) L*a*b* uniform color system. The results revealed the presence of rutile inclusions in color-changing garnet. Strong absorption in both the blue-violet zone and orange-yellow zone was the main cause for the color-changing effect of garnet. The distribution pattern of rare earth elements (REE) was left-leaning, showing the enrichment of heavy rare earth elements (HREE) and depletion of light rare earth elements (LREE). As the total Cr and V concentrations increased, the area of the 574 nm absorption peak in the UV-Vis spectrum also increased, leading to a more significant variation in color ΔE*ab. The light path length of the gemstone had a significant impact on the extent of the color-changing effect. The color difference reached a maximum and the color-changing effect was most visible when the thickness of the gemstone was 5 mm.

Tracing Gadolinium levels throughout wastewater treatment: Insights from a yearly assessment in northern Spain

Gadolinium (Gd) is a rare earth element (REE) used in the formulation of contrast agents for Magnetic Resonance Imaging (MRI) due to its paramagnetic properties. The growth in population and the improved quality of the healthcare systems over the last years, has promoted the use of MRI as an effective diagnostic tool thus increasing the consumption of gadolinium and its release into the wastewater treatment network. Therefore, the tracking and quantification of this metal in sewage treatment plants and water bodies, is of paramount importance since there are currently no specific rare earth treatment technologies installed in WWTPs, and consequently gadolinium is finally discharged into the environment. In this work, the presence of gadolinium and all other rare earth elements was monitored during a year in three WWTPs in northern Spain (Vuelta Ostrera and San Román in Cantabria and Galindo in País Vasco). These WWTPs are located close to urban centres with hospitals where MRI tests are performed. By tracing Gd throughout the wastewater treatment facilities, its presence was confirmed in water streams, in the order of ng per litter, and in sludge and ashes, in the order of mg per kilogram. A significant human influence was observed, with Gd anomaly values between 3.14 and 79.2 and anthropogenic Gd percentages above 90 %. The presence of Gd in water streams is affected by the sampling period due to the variations of the activity periods of the hospitals nearby the treatment plants. On the contrary, its content in sludge and ashes remains almost constant along the year. The concentration of this metal found in the ashes opens the door to its possible recovery together with other critical raw materials in the context of the circular economy.

Discovery of a giant lattice in Mg97Zn1Yb2 alloy

The Mg-rich corner of Mg–metal (M)–rare earth element (REE) ternary systems results in a long-period stacking-ordered (LPSO) phase that increases the strength and elongation of the Mg alloy. Using Yb at the REE position does not result in the LPSO phase; instead, it forms unique crystalline structures with intriguing properties. In this study, we found a new giant lattice belonging to the P6/mmc space group by quenching the Mg97Zn1Yb2 alloy at 723K. The giant lattice, which precipitates around the α-Mg matrix with a chemical composition of Mg75Zn7Yb18 (at.%), comprises a basic structure and a superlattice. We developed an atomic configuration model that expresses the basic structure as alternating stacking of three types of layers. The observed features indicate that the structure of the giant lattice is similar to that of the approximant quasicrystal reported for Mg–M–REE ternary systems.

New discovery of the Early Paleozoic carbonatite in Bayan Obo (China): Insights into the giant REE accumulation

The Bayan Obo deposit in China hosts the world’s largest rare earth element (REE) resource. Age dating results for Bayan Obo range across approximately one billion years (from ∼1.4 to 0.3 Ga), with three age groups (∼1.3 Ga, ∼0.45–0.40 Ga, and 0.28–0.26 Ga). Carbonatite dated to around 1.3 Ga and granitoids to approximately 270 Ma have been identified. The Early Paleozoic vein-type mineralization is widespread in the deposit. However, magmatic activity related to the highest age peak at ∼0.4 Ga has not well been identified in the deposit, complicating the interpretation of the ore genesis. In this study, we report a zircon 232Th-208Pb age of 435.2 ± 4.6 Ma (MSWD = 1.9, N = 26) from carbonatite in Bayan Obo. The zircon morphology, characterized by bipyramidal crystal forms, low U concentrations (mostly < 1 ppm), high Th/U ratio, and carbonatite-like oxygen isotopes (5.92 ± 0.31 ‰), demonstrates that the zircon crystallized from carbonatitic magmas, thus their ages represent the timing of magmatic activity. Although remelting of the Mesoproterozoic carbonatite during Paleozoic carbonatite has been previously documented, the newly identified Early Paleozoic carbonatite derives from a different mantle source, as indicated by their more radiogenic Hf isotope compositions. This suggests that the Bayan Obo deposit experienced multiple carbonatitic activities. The Early Paleozoic carbonatitic activity may have facilitated element mobilization and mineral recrystallization, improving the exploitable levels of the world’s largest REE deposit.

Predominance of Yb3+ and Ce3+ on the AlTaBaBO: Yb and BaTiSbBPO: Ce glasses for effective photoluminescence and radiation shielding properties towards w-LED and γ-ray shielding applications

Alumino tantalum barium borate - 65B2O3 +10Al2O3 +5SrCO3 +5BaCO3 +14Li2CO3 +4Ta2O5 +1Yb2O3 (AlTaBaBO: Yb) and barium antimony borophosphate - 35P2O5 +35B2O3 +10TiO2 +5KF +10Li2CO3 +4SbO3 +1CeO3 (BaTiSbBPO: Ce) glasses were prepared using melt – quenching technique. The structural property of as-prepared glass materials is investigated by powder X–ray diffraction to identify the amorphous nature of the materials. FTIR and FT-Raman spectroscopic analyses examined various functional groups of glasses. The linear optical behaviours were characterized using UV-visible spectroscopy, and besides the different linear optical parameters such as refractive index and optical bandgap, optical conductivity was estimated. Excitation and emission spectra of the harvested glasses were characterized using a Photoluminescence spectrophotometer. Rare earth – R.E (Yb3+ and Ce3+) doped both glasses have greater emission efficiency due to their 2F7/2 → 2F5/2 (951 nm) and 5d1 → 2F5/2, 2F7/2 (550 and 663 nm) electronic transitions, which shows that the as-prepared glass materials have their potential applications. Colour chromaticity (CIE) diagrams of the cultivated glasses were examined with colour co – ordinations x = 0.3054, y = 0.2881 for AlTaBaBO: Yb and x = 0. 3874, y = 0.3436 for BaTiSbBPO: Ce and the obtained outcomes confirmed w-LED device fabrication. Moreover, the various γ– ray shielding parameters were analyzed theoretically using Phy-X software. The five (a, b, c, d, and Xk) parameters of the Geometric Progression (G-P) fitting scheme were used to determine the energy-related energy buildup factor (EBF) as well as energy absorption buildup factor (EABF) of glasses in terms of infiltration deepness up to 40 mfp. At lower photon energy, the AlTaBaBO: Yb and BaTiSbBPO: Ce glasses have the highest μ/ρ values of 4.47 x105 cm2/g and 3.864 x103 cm2/g, respectively. For AlTaBaBO: Yb and BaTiSbBPO: Ce glasses, the calculated mean free path (MFP) values at 15 MeV photon energy are 0.143 cm and 12.18 cm, respectively. The result of all findings reveals that the synthesized glasses are viable materials for the futuristic utilization of w-LED and neutron radiation shielding applications.

Unveiling the enhancing mechanism of cyclic stability in Tb doped Ni-Mn-Sn Heusler alloys

Rare-earth (RE) doping has been demonstrated as a feasible approach to improve the cyclic performance of Ni-Mn-based Heusler alloys, but the current demonstration of underlying mechanism is simply ascribed to strengthening of the grain boundary cohesion. In this work, the effects brought by RE doping on microstructure, stress induced martensitic transformation behavior and cyclic stability of Ni-Mn-based alloys were systematically investigated. By Tb doping, a stable adiabatic temperature change (|ΔTad|) of ∼ 5.5 K over 1000 cycles with no significant degradation was obtained in (Ni43Mn47Sn10)99.5Tb0.5. (1) Through the in-situ digital image correlation strain measurement and in-situ SEM observation upon loading process, it revealed a multipoint nucleation of the martensitic transformation across the specimen arising from the intergranular NiSnTb secondary phase as nucleate sites, which weakens the strain concentration and suppresses the crack tendency. (2) The multipoint nucleation promotes the transformation volume fraction, making the large |ΔTad| could be driven by a small transformation strain (Δεtr) and (Ni43Mn47Sn10)99.5Tb0.5 yields a |ΔTad/Δεtr| up to 8.7 K %−1. Such reduction in applied strain further alleviates the extension of the cracks. Both the two factors brought by Tb doping in (Ni43Mn47Sn10)99.5Tb0.5 give rise to the enhancement in cyclic stability of the large elastocaloric effect.