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The study makes three recommendations to enhance ASEAN's role in the critical minerals supply chains. The first addresses the insufficiency of investments in early-stage exploration and exploitation of critical minerals and, in the process, calls for an embracing of circular economy principles. The second appeals for investments at all stages, including in technology to tap into downstream activities beyond refining and purification, and in the manufacturing of component parts such as battery cell storage and permanent magnets. The third calls for improvements in sustainability management in the mining sector, which is generally extremely environmentally and socially damaging to communities.

Direct thermal decomposition of rare-earth chlorides into rare-earth oxides (REOs) in a single step presents a short-process, wastewater-free, and environmentally friendly alternative to the conventional precipitation–calcination method, which produces large amounts of saline wastewater. While earlier reviews have primarily focused on summarizing reaction conditions and thermodynamic parameters, they have seldom discussed the critical variations in pyrolysis behavior across different rare-earth elements. This review highlights a novel classification of rare-earth chlorides into fixed-valence and variable-valence groups, revealing how their respective oxidation states govern thermodynamic stability, reaction pathways, and chlorine release behavior. Furthermore, a systematic comparison is provided on the effects of additives, temperature, and gas partial pressure on product purity, particle size, and microstructure, with particular attention to the mechanisms underlying oxychloride intermediate formation. Beyond fundamental reaction principles, this work uniquely evaluates the design and performance of existing pyrolysis reactors, outlining both opportunities and challenges in scaling up direct rare-earth chloride (REClx) pyrolysis for industrial REO production. By integrating mechanistic insights with reactor engineering considerations, this review offers advancements over previous descriptive summaries and proposes a strategic pathway toward sustainable rare-earth processing.

A series of rare-earth (Ce, La, Nd, and Y) oxides doped Mn/Al 2 O 3 catalysts were prepared by the impregnation method and used for the selective catalytic reduction (SCR) of NO x with NH 3 . The additions of rare-earth oxides greatly enhance the SCR catalytic activity of Mn/Al 2 O 3 , and the highest activity was obtained over CeMn/Al 2 O 3 with a NO x conversion higher than 85% at 125–300 °C. The results of characterization show that the rare-earth oxides additives except for Y 2 O 3 promote the surface distribution of Mn element and enhance the ratio of chemisorbed oxygen and Mn 4+ on the surface of Mn/Al 2 O 3 . Moreover, with the introduction of rare-earth oxides, the reducibility of MnO 2 species is improved and a larger amount of the weak acid sites are obtained. The increase in the ratio of Mn 4+ and the enhancement in the reducibility of MnO 2 are the main reasons for the elevation in SCR activity of the rare-earth oxides modified Mn/Al 2 O 3 catalysts. This study sheds light on the promotional effect of rare-earth oxides over the Mn-based catalysts for SCR reaction. Graphical Abstract Rare-earth oxides greatly enhance the SCR catalytic activity of Mn/Al 2 O 3 , and the highest activity was obtained over CeMn/Al 2 O 3 with a NO x conversion higher than 85% at 125–300 °C.

The elimination of inclusions in steelmaking processes has been widely studied. The removal of inclusions by slags containing the rare earth oxide Ce2O3 are studied using an integrated numerical model. The integrated model involves the inclusion motion model, interfacial tension calculation model, surface tension calculation model of slag, and the mass action concentration model, based on ion and molecule coexistence theory. The motion behaviors of both solid Al2O3 inclusions and 50%wtAl2O3–50%wtCaO liquid inclusions of varied sizes at CaO-Ce2O3-SiO2-Al2O3(-MgO) slag systems are evaluated. The results show that it is more difficult to remove the inclusions with smaller sizes and in slag with a higher viscosity. Liquid inclusions are more difficult to remove than solid inclusions. It is found that the CaO-Ce2O3-SiO2-Al2O3-MgO refining slag shows a better ability to remove Al2O3 inclusions than that of the CaO-SiO2-Al2O3-MgO slag. The reason for this is that the addition of the rare earth oxide Ce2O3 can decrease the viscosity of slags, as well as improving the wetting effects of slags on Al2O3 inclusions. For two slags systems, the CaO-Ce2O3-SiO2-Al2O3-MgO slag system shows a better ability to remove Al2O3 inclusions than the CaO-Ce2O3-SiO2-Al2O3 slag system. The addition of 5% to 8% Ce2O3 in a CaO-SiO2-Al2O3-MgO slag is an optimized case for industrial applications.

Aerogels containing rare earth elements are promising compounds for designing various functional materials, since they combine the properties of aerogels - high surface area and porosity, and the luminescent and catalytic properties of rare earth elements. A modified sol-gel method was developed to produce mixed rare earth oxide aerogels (Eu 2 O 3 /Gd 2 O 3 , Eu 2 O 3 /Yb 2 O 3 , and Gd 2 O 3 /Yb 2 O 3 ) with high metal to metal molar ratio (1:1) and individual (Eu 2 O 3 , Gd 2 O 3 , and Yb 2 O 3 ) aerogels. Rare earth nitrates, propylene oxide, and citric acid were used for the synthesis of monolithic halogen-free rare earth oxide aerogels. The aerogels obtained by supercritical drying in CO 2 possess mesoporous structure and high surface area (180–350 m 2 /g). Uniform distribution of elements in binary oxides was confirmed by EDX. Calcination at 600–800 °С causes crystallization of the amorphous aerogels. XRD patterns of the binary oxides after calcination corresponded to single phase cubic ( I a 3 ¯ ) structure of rare earth M 2 O 3 oxide, which indicated the formation of solid solutions. The Eu 2 O 3 /Gd 2 O 3 and Eu 2 O 3 aerogels demonstrate strong luminescence in visible region at near UV excitation, which was also observed after calcination of the aerogels at 800 °C. Graphical Abstract For the first time mixed aerogels (Eu 2 O 3 /Gd 2 O 3 , Eu 2 O 3 /Yb 2 O 3 , and Gd 2 O 3 /Yb 2 O 3 ) with high metal to metal molar ratio (1/1) were obtained by propylene oxide assisted hydrolysis of RE nitrates in presence of citric acid as a chelating agent. The aerogels after SC drying in CO 2 possess mesoporous structure with high surface area. Calcined at 600–800 °С aerogels have cubic lattice ( I a 3 ¯ ) of rare earth sesquioxide with crystallites diameter about 20–40 nm. XRD, IR spectroscopy and EDX analysis reveal uniform distribution of elements in material and formation of solid solutions after calcination of the mixed RE oxides. The Eu 2 O 3 /Gd 2 O 3 aerogels demonstrate red luminescence under near UV excitation. Highlights Binary (Eu 2 O 3 /Gd 2 O 3 , Eu 2 O 3 /Yb 2 O 3 , and Gd 2 O 3 /Yb 2 O 3 ) and individual (Eu 2 O 3 , Gd 2 O 3 , and Yb 2 O 3 ) aerogels with high surface areas were synthesized by supercritical drying in CO 2 . Influence of propylene oxide and citric acid concentrations on sol-gel process in RE nitrate solutions was studied. After calcination at 600–800 °С the amorphous aerogels get crystalline structure, the binary oxides demonstrate single phase. The binary and individual oxides were characterized by XRD, IR, nitrogen absorption, SEM methods. The as-prepared and calcinated europium-containing aerogels demonstrate luminescence in visible region at near UV excitation.

Background Disruption of microbiota balance may result in severe diseases in animals and phytotoxicity in plants. While substantial concerns have been raised on engineered nanomaterial (ENM) induced hazard effects (e.g. , lung inflammation), exploration of the impacts of ENMs on microbiota balance holds great implications. Results This study found that rare earth oxide nanoparticles (REOs) among 19 ENMs showed severe toxicity in Gram-negative (G − ) bacteria, but negligible effects in Gram-positive (G + ) bacteria. This distinct cytotoxicity was disclosed to associate with the different molecular initiating events of REOs in G − and G + strains. La 2 O 3 as a representative REOs was demonstrated to transform into LaPO 4 on G − cell membranes and induce 8.3% dephosphorylation of phospholipids. Molecular dynamics simulations revealed the dephosphorylation induced more than 2-fold increments of phospholipid diffusion constant and an unordered configuration in membranes, eliciting the increments of membrane fluidity and permeability. Notably, the ratios of G − /G + reduced from 1.56 to 1.10 in bronchoalveolar lavage fluid from the mice with La 2 O 3 exposure. Finally, we demonstrated that both IL-6 and neutrophil cells showed strong correlations with G − /G + ratios, evidenced by their correlation coefficients with 0.83 and 0.92, respectively. Conclusions This study deciphered the distinct toxic mechanisms of La 2 O 3 as a representative REO in G − and G + bacteria and disclosed that La 2 O 3 -induced membrane damages of G − cells cumulated into pulmonary microbiota imbalance exhibiting synergistic pulmonary toxicity. Overall, these findings offered new insights to understand the hazard effects induced by REOs.

Conventional Fe-C alloy parts used in mechanical transmission and braking systems exposed to the external environment often suffer from wear and corrosion failures. Surface coating strengthening technologies have been explored to improve the surface performance and prolong service life of these parts. Among these technologies, laser cladding has shown promise in producing Fe-based alloy coatings with superior interfacial bonding properties to the Fe-C alloy substrate. Additionally, the microstructure of the Fe-based alloy coating is more uniform and the grain size is finer than that of surfacing welding, thermal spraying, and plasma cladding, and the oxide film of alloying elements on the coating surface can improve the coating performance. However, Fe-based alloy coatings produced by laser cladding typically exhibit lower hardness, lower wear resistance, corrosion resistance, and oxidation resistance compared to coatings based on Co and Ni alloys. Moreover, these coatings are susceptible to defects such as pores and cracks. To address these limitations, the incorporation of rare-earth oxides through doping in the laser cladding process has garnered significant attention. This approach has demonstrated substantial improvements in the microstructure and properties of Fe-based alloy coatings. This paper reviewed recent research on the structure and properties of laser-cladded Fe-based alloy coatings doped with various rare earth oxides, including La 2 O 3 , CeO 2 , and Y 2 O 3 . Specifically, it discussed the effects of rare earth oxides and their concentrations on the structure, hardness, friction, wear, corrosion, and oxidation characteristics of these coatings. Furthermore, the mechanisms by which rare earth oxides influence the coating’s structure and properties were summarized. This review aimed to serve as a valuable reference for the application and advancement of laser cladding technology for rare earth modified Fe-based alloy coatings.

A novel series of glass, consisting of B2O3, Bi2O3, TeO2, and TiO2 (BBTT) containing rare earth oxide RE2O3, where RE is La, Ce, Sm, Er, and Yb, was prepared. We investigated the structural, optical, and gamma attenuation properties of the resultant glass. The optical energy bands, the linear refractive indices, the molar refractions, the metallization criteria, and the optical basicity were all determined for the prepared glass. Furthermore, physical parameters such as the density, the molar volume, the oxygen molar volume, and the oxygen packing density of the prepared glass, were computed. Both the values of density and optical energy of the prepared glass increased in the order of La2O3, Ce2O3, Sm2O3, Er2O3, and then Yb2O3. In addition, the glass doped with Yb2O3 had the lowest refractive index, electronic polarizability, and optical basicity values compared with the other prepared glass. The structures of the prepared glass were investigated by the deconvolution of infrared spectroscopy, which determined that TeO4, TeO3, BO4, BO3, BiO6, and TiO4 units had formed. Furthermore, the structural changes in glass are related to the ratio of the intensity of TeO4/TeO3, depending on the type of rare earth. It is also clarified that the resultant glass samples are good attenuators against low-energy radiation, especially those that modified by Yb2O3, which exhibited superior shielding efficiency at energies of 622, 1170, and 1330 keV. The optical and gamma ray spectroscopy results of the prepared glass show that it is a good candidate for nonlinear optical fibers, laser solid material, and optical shielding protection.

This study involved the preparation of natural rubber-based composites incorporating varying proportions of heavy metals and rare earth oxides (Sm2O3, Ta2O5, and Bi2O3). The investigation analyzed several parameters of the samples, including mass attenuation coefficients (general, photoelectric absorption, and scattering), linear attenuation coefficients (μ), half-value layers (HVLs), tenth-value layers (TVLs), mean free paths (MFPs), and radiation protection efficiencies (RPEs), utilizing the Monte Carlo simulation software Geant4 and the WinXCom database across a gamma-ray energy spectrum of 40–150 keV. The study also compared the computational discrepancies among these measurements. Compared to rubber composites doped with single-component fillers, multi-component mixed shielding materials significantly mitigate the shielding deficiencies observed with single-component materials, thereby broadening the γ-ray energy spectrum for which the composites provide effective shielding. Subsequently, the simulation outcomes were juxtaposed with experimental data derived from a 133Ba (80 keV) γ-source. The findings reveal that the simulated results align closely with the experimental observations. When compared to the WinXCom database, the Geant4 software demonstrates superior accuracy in deriving radiation shielding parameters and notably enhances experimental efficiency.