Small Amounts Of Rare Earth Elements Research Articles

Selective Dissolution of Nd2O3 from the Mixture with Fe2O3 and Ga2O3 by Using Inorganic Acid Solutions Containing Ethylene Glycol

Rare earth elements (REEs) are strategically critical in the manufacture of advanced materials. Red mud and end-of-life NdFeB magnets can be good secondary sources for REEs, but recovery is difficult due to the high iron oxide content and small amount of REEs. Oxide mixtures whose composition of Fe, Nd, and Ga was similar to that in red mud were employed in experiments. In this study, a relatively inexpensive non-aqueous system was used to selectively dissolve Nd2O3 in a mixture with Fe2O3 and Ga2O3. The addition of ethylene glycol (EG) to HCl and H2SO4 solution depressed the dissolution of Fe2O3 and Ga2O3 from the mixtures, and thus selective dissolution of Nd2O3 was possible. The optimum conditions were as follows: (a) 1.0 M HCl in EG, 25 °C ± 1 °C, 50 g/L pulp density, 120 min, 200 rpm; and (b) 0.05 M H2SO4 in EG, 25 °C ± 1 °C, 50 g/L pulp density, 60 min, 300 rpm. Under these conditions, Nd2O3 was completely dissolved, whereas no Fe2O3 or Ga2O3 was dissolved by the H2SO4 system, and the dissolution percentage of these two oxides by the HCl system was less than 1%. Due to the selective dissolution of Nd2O3 from the oxide mixtures, it is simple to recover Nd. An efficient process can be developed for the recovery of REEs from red mud and end-of-life NdFeB magnets by applying our results.

Effect of Rare Earth Elements on the Morphology of Eutectic Carbides in AISI D2 Tool Steels: Experimental and Modelling Approaches

The morphology of the eutectic chromium carbides in the microstructure of as-cast AISI D2 tool steel was modified by adding small amounts of rare-earth elements (REEs) to the melt. As a result of these REE additions the eutectic carbide morphological type was changed from lamellar to globular. Similar phenomena have already been reported for various tool steels, but no complete theoretical explanation has been provided. Here, we propose a new model that is derived from first-principles thermodynamic calculations based on the phase-field modeling of the eutectic reaction. Using this new approach, where the decomposition of the phase-boundary surface-energy term is divided into the isotropic and anisotropic parts, we were able to account for the transition from a lamellar to a globular eutectic morphology in REE-modified AISI D2 tool steel.

Universal solders for direct bonding and packaging of optical devices

For optical packaging, there is a need to directly bond non-solderable materials such as oxides, nitrides, borides and fluorides, which are very difficult to wet/bond with low melting point solders, for example, at ~150°C or below. In this research, we describe new Pb-free universal solders with low melting point of 140°C or below by doping with a small amount of rare-earth elements, especially inexpensive mischmetals, which allow direct and powerful bonding onto the surfaces of various optical and electronic devices. The microstructure of the solder bonds is described, and their potential applications for passive and active optical components assembly are discussed.

Effects of rare earth additions during surface boriding on microstructure and properties of titanium alloy TC21

In the present paper, the effects of rare earth (RE) additions to the solid state boriding of titanium alloy TC21 have been studied. The microstructural evolution and phase transformations of the borided layers were examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. Moreover, the microhardness for the borided layer was also determined by Vickers hardness test. The results showed that the addition of a small amount of RE elements in the boriding process can lead to an increased boron concentration in the surface layer coupled with the improved surface hardness and coating layer thickness. Furthermore, the presence of trace quantities of RE oxide (Ce2O3) in boride layers indicated that the RE elements as catalysts could not only influence but also accelerate boriding process.

Heat capacity of BiFeO3-based multiferroics

The heat capacity of Bi1 − x Re x FeO3 (Re = La, Eu, Ho; x = 0, x = 0.05) multiferroics has been studied in the temperature range of 120–800 K. The substitution of a small amount of rare-earth elements for bismuth leads to a significant increase in the heat capacity in the broad temperature range studied. It is established that the temperature dependence of the excess heat capacity is related to the Schottky effect for three-level states certain that appear as a result of structure distortions in the rare-earth-doped compositions.

Influence of rare earth elements on the acid and metal sites of Pt/HBEA catalyst for short chain n-alkane hydroisomerization

The doping effect of rare earth (RE) elements La, Nd and Yb on the acidity and metal function of Pt/HBEA catalysts was investigated, as well as its influence in the hydroisomerization of n-hexane. HBEA zeolite was submitted to ion exchange with increasing amounts of RE using nitrate solutions, followed by Pt introduction. The samples were characterized by powder X-ray diffraction, chemical analysis and low temperature N2 adsorption. The acidity of the samples was study through pyridine adsorption followed by FTIR spectroscopy and the model reaction of n-heptane cracking. The influence of RE elements on the metal function was studied by magnetic susceptibility measurements, model reaction of toluene hydrogenation and H2 chemisorption analysis. The characterization methods showed that the presence of very small amounts of RE elements increases the strength and density of the acid sites due to the appearance of new Lewis acid sites that are detected upon RE loading. The electronic properties and metal dispersion of Pt were also improved. In n-hexane hydroisomerization reaction an increased catalytic activity and selectivity into dibranched isomers is detected in the presence of very low contents of La and Nd (less than 0.4wt.%). For higher amounts and also in the case of Yb doped samples, where the amounts introduced were higher, a decrease in catalytic activity as well as a higher selectivity in cracking products is noticed as a result of stereochemical limitations inside the zeolite pore structure.

Geochemical characteristics of rare earth elements (REEs) in the paddy soil and rice (Oryza sativa L.) system of Kočani Field, Republic of Macedonia

In the Republic of Macedonia, information about rare earth elements (REEs) distribution patterns, transportation and speciation characteristics (from soil to plants) is very rare. Therefore, the concentrations of REEs in Kočani paddy soils and rice samples from the Republic of Macedonia were measured and evaluated. The elevated concentrations of REEs in paddy soils can be explained by contributions from acidic and intermediate igneous rocks, which are one of the main source materials for Kočani paddy soils. Low percentages of REEs were bound to the water-soluble and exchangeable fractions, revealing low mobility of REEs in the investigated paddy soils. Furthermore, small amounts of REEs were detected in rice (Oryza sativa L.) grain samples. The calculated transfer values (TF) for REEs in rice samples were also very low, confirming a small accumulation of REEs (La, Ce, Pr, Nd and Sm) by the studied crops and in the Kočani soil–plant system.

Effects of the accumulation of the rare earth elements on soil macrofauna community

The accumulation of rare earth elements (REEs) in soil has occurred due to the pollution caused by the exploitation of rare earth resources and the wide rare earth fertilizers in agriculture. The accumulation of REEs has a toxic effect on the soil macrofauna community. 12 study samples were collected near a mine tailings dam with a large amount of REEs by distance gradient sample method. The total concentration of REEs was analyzed and the results were compared with that of the sample from a control site. The effects of the amount of REEs in the soil on the soil macrofauna community were also analyzed. The results showed that the accumulation of REEs in soil was significant in the study area and its concentration was strongly correlated with the distance from the pollution source. One-way ANOVA analysis indicated the significant differences in soil macrofauna communities among the different sites. The ordination obtained through the redundancy analysis demonstrated that the concentration of REEs and the total nitrogen, total potassium and pH, had affected the soil macrofauna community. A small amount of REEs in the soil can promote the diversity of soil macrofauna, but a large amount of REEs can reduce its diversity. The insect groups of Carabidae and Dermaptera were comparatively sensitive to the concentration of REEs in soil, and could be used as an indicator of soil pollution of REEs. However, the Formicidae and Stibaropus formosanus exhibited a high tolerance to REEs in soil. We believe that it is very important for the soil environment protection to strictly control the application of the rare earth fertilizers in agriculture in China.

Microwave absorbing properties of rare-earth elements substituted W-type barium ferrite

W-type barium ferrites Ba(MnZn) 0.3Co 1.4R 0.01Fe 15.99O 27 with R=Dy, Nd and Pr were prepared by chemical coprecipitation method. Effects of rare-earth elements (RE) substitution on microstructural and electromagnetic properties were analyzed. The results show that a small amount of RE 3+ ions can replace Fe 3+ ions and adjust hyperfine parameters. An obvious increase in natural resonance frequency and high frequency relaxation, and a sharp decrease for complex permittivity have been observed. Furthermore, the matching thickness and the reflection loss (RL) of one-layer ferrite absorber were calculated. It reveals that thin and broad-band can be obtained by RE-substitution. But only when the magnetic moment of RE 3+ is higher than that of Fe 3+, can substitution be effective for higher RL. Dy-substituted ferrite composite has excellent microwave absorption properties. The frequency (with respect to −10 dB RL) begins from 9.9 GHz, and the bandwidth reaches far more than 8.16 GHz. The peak value is −51.92 dB at a matching thickness of 2.1 mm.

Removal of rare earth elements by algal flagellate Euglena gracilis

Removal of rare earth elements (REEs) from an acid solution by an algal flagellate, Euglena gracilis, was studied. Sixteen kinds of REEs were spiked to the solution at a final concentration of 10 μg L −1 for each element. E. gracilis cells grown in the solution under 12 h light–dark cycles efficiently removed REEs during the 21-day experimental period. Significant removal was observed from days 14 to 21 of incubation. On the last day, concentrations of REEs were less than 0.7 μg L −1 except for Sc. The concentration of Sc was 2.8 ± 0.4 μg L −1, suggesting that Sc removal was relatively difficult compared to the other REEs. Among REEs, the same level of removal was observed for light REEs (La–Eu) but not for heavy REEs (Ga–Lu). Heavy REEs removal tended to decrease with an increase in atomic number. The removal of REEs by E. gracilis were affected by lighting conditions because E. gracilis cells grown in the dark had removed just a small amount of REEs, less than 10% of total, through day 21 of incubation.

Allanite and Other REE-Rich Epidote-Group Minerals

Research Article| January 02, 2004 Allanite and Other REE-Rich Epidote-Group Minerals Reto Gieré; Reto Gieré Institut für Mineralogie, Petrologie und Geochemie, Universität Freiburg, Albertstrasse 23b, D-79104 Freiburg, Germany, giere@uni-freiburg.de Search for other works by this author on: GSW Google Scholar Sorena S. Sorensen Sorena S. Sorensen Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, U.S.A., sorena@volcano.si.edu Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2004) 56 (1): 431–493. https://doi.org/10.2138/gsrmg.56.1.431 Article history first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Reto Gieré, Sorena S. Sorensen; Allanite and Other REE-Rich Epidote-Group Minerals. Reviews in Mineralogy and Geochemistry 2004;; 56 (1): 431–493. doi: https://doi.org/10.2138/gsrmg.56.1.431 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyReviews in Mineralogy and Geochemistry Search Advanced Search Epidote-group minerals rich in rare earth elements (REE), in particular allanite, are common accessory phases in igneous, metamorphic, metasomatic, and sedimentary rocks. Small amounts of REE are present in most epidote-group minerals, but in allanite—and the related minerals dissakisite, ferriallanite, dollaseite, khristovite and androsite—the REE are essential structural constituents. An important characteristic of REE-rich epidote-group minerals is that their octahedrally coordinated M sites contain major amounts of divalent cations. This paper summarizes literature data for these minerals and discusses their chemistry, occurrence, phase relations, and petrologic and geologic significance. The chapter emphasizes allanite, because it is the most common and... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

EFFECTS OF RARE-EARTH ELEMENT La ON GLASS FORM-ING ABILITY AND T HERMOST ABILITY OF Ni-B-Si METALLIC GLASS

Small amount of rare-earth elements may have negative effects on the formation of some metallic glass alloys. The rare-earth elements may react with some atoms of the alloys to form compounds of high melting points or be absorbed on the surfaces of the heterogeneous catalysts in the alloys to activate the heterogeneous nucleation. In this case, the rare-earth elements have no effects on enhancing the stability of the metallic glass phase but enhance the heterogeneous nucleation and decrease the metallic glass forming ability and thermostability.