Effects Of Rare Earth Elements Research Articles

Effect of rare earth elements on the structural, magnetic and electrical behavior of Ni-Zn-Cr nanoferrites

Mixed nickel-zinc-chromium ferrites having the general formula Ni0.7Zn0.3CrxRyFe2-x-yO4 (where x = 0.5, y = 0.02 and R = Gd3+, Sm3+ and Ce3+) were prepared, for the first time by using auto-combustion method at low sintering temperature (523 K). X-ray diffraction (XRD) analysis and Fourier transform infrared spectrum (FT-IR) confirmed the formation of single phase spinel structure in all the samples. The variations of the lattice parameter and particle size were discussed in the view of ionic radii. High resolution transition electron microscope (HT-TEM) and scan electron microscopy (SEM) images showed spherical and elongated shapes of the nanoparticles where the average particle size ranged 13–17 nm. The vibrating sample magnetometer (VSM) measurements confirmed a strong influence of rare earth doping on the saturation magnetization (Ms) and coercivity (Hc) due to the preferential occupation of RE ions in the octahedral B-sites. The magnetic parameters suggested that these nano-materials are suitable for technological application. The dielectric parameters (ε׳, ε″ and tanδ) and electrical conductivity (σ) were measured at different temperatures in the frequency range (102–105Hz). The electrical conductivity of the sample ferrite doped with Gd was showing semi-conducting behavior while for the samples doped with Ce and Sm, semi-conductor to semi-metallic were observed. The dielectric loss (tanδ) and dielectric constant (ɛ) show that these materials are useful in high frequency applications.

Research on Sensitization Effect of Ceria Nanoparticles on Tin Oxide Wire-in-Tube Nanofibers

To elaborate the effect of CeO2 nanoparticles on the sensing properties of SnO2, CeO2-functionalized SnO2 wire-in-tube nanofibers (WITN) was prepared by electrospinning and subsequently impregnating treatment. The gas sensing studies revealed that the CeO2 loaded SnO2 WITN exhibited enhanced sensitivity to ethanol compared to the pristine SnO2. With increasing amount of CeO2, the response of nanocomposites increases firstly and then decreases. And the response of nanocomposites to ethanol reach maximum when the concentration of impregnated Ce (NO3)3·6H2O is 0.03 mol·L-1. To detail the sensing mechanism, the X-ray photoelectron spectroscopy was firstly employed to detect the variation in oxygen species corresponding to different amounts of CeO2, but no obviously changes in oxygen species was detected. Subsequently, it was found that the initial resistance of CeO2@SnO2 WITN was higher than pristine SnO2, which could be beneficial to the improvement of sensing properties. More importantly, oxygen vacancy (mainly offered by CeO2 nanoparticles) was proved to be positively correlated to their gas-sensing performance. In this work, the electronic sensitization mechanism based on CeO2 loaded SnO2 was detailed, which could help for the better understanding the sensitization effect of rare earth element on semiconductor oxides.

Effects of rare earth elements on growth rate, lipids, fatty acids and pigments in microalgae

SUMMARYThe extensive exploitation of rare earth elements (REEs), particularly in electronic technologies and agriculture has concomitantly raised the environmental load. Their resulting effects on primary producers such as microalgae are, however, poorly understood. We have studied these effects on two microalgae of biotechnological interest. The yellow‐green alga Trachydiscus minutus (Eustigmatophyceae, Ochrophyta), and the green alga Parachlorella kessleri (Trebouxiophyceae, Chlorophyta) were cultivated in mineral medium supplemented with 10 μmol L−1 chlorides of REEs: cerium, gadolinium, lanthanum, lutetium, praseodymium, scandium, and with monazite, which is a mineral rich in those elements. We observed growth rates at different mean light intensities (20, 50, 150 and 300 μmol m−2 s−1). The high growth rate of P. kessleri was not affected by the presence of any lanthanide, and decreased proportionally with light intensity (from 0.2 to 0.04 doublings per hour). In contrast, the growth rate of T. minutus was about three times lower compared with P. kessleri, with an optimum at 50 μmol m−2 s−1 and decreased at higher or lower light intensities. In the presence of Ce3+, La3+ and Sc3+, the growth rate markedly increased to a value that corresponded to the growth rate in P. kessleri at the same light intensity. The composition and content of pigments and lipids were followed at the optimum light intensity for both species. The lipid content (percentage of dry weight) varied only slightly in the presence of individual rare earths. There was, however, an increase in saturated fatty acids at the expense of polyunsaturated fatty acids. The effect of REEs on pigments was variable: the presence of Ce3+, Gd3+, La3+ and Sc3+ caused an increase in the concentrations of major pigments such as lutein, violaxanthin, β‐carotene or chlorophylls, while Pr3+ and Lu3+ reduced them.

Effects of Rare Earth Elements on Properties of Ni-Base Superalloy Powders and Coatings

NiCrMoY alloy powders were prepared using inert gas atomization by incorporation of rare earth elements, such as Mo, Nb, and Y into Ni60A powders, the coatings were sprayed by oxy-acetylene flame spray and then remelted with high-frequency induction. The morphologies, hollow particle ratio, particle-size distribution, apparent density, flowability, and the oxygen content of the NiCrMoY alloy powders were investigated, and the microstructure and hardness of the coatings were evaluated by optical microscopy (OM). Due to incorporation of the rare earth elements of Mo, Nb, or Y, the majority of the NiCrMoY alloy particles are near-spherical, the minority of which have small satellites, the surface of the particles is smoother and hollow particles are fewer, the particles exhibit larger apparent density and lower flowability than those of particles without incorporation, i.e., Ni60A powders, and particle-size distribution exhibits a single peak and fits normal distribution. The microstructure of the NiCrMoY alloy coatings exhibits finer structure and Rockwell hardness HRC of 60–63 in which the bulk- and needle-like hard phases are formed.

Effect of rare earth element on the oxidation behavior of novel γ/γ′-strengthened Co–9Al–10W alloys

Abstract

稀土La<sub>2</sub>O<sub>3</sub>对激光熔覆316 L合金粉末熔覆层性能的影响

稀土具有细化激光熔覆层晶粒、强化激光熔覆层强度、抑制激光熔覆层枝晶生长的作用。本文选取316 L不锈钢粉末为熔覆材料, 并加入稀土氧化物La2O3进行变质处理，在1Cr18Ni9Ti不锈钢基体表面进行激光熔覆实验，对比分析熔覆层组织，并进行耐腐蚀实验，分析稀土含量对熔覆层硬度的影响，研究稀土元素对激光熔覆层的影响。 Rare earth has the effect of refining the grain of laser cladding layer, strengthening the intensity of laser cladding layer and restraining the dendrite growth of laser cladding layer. In this paper, 316 L stainless steel powder was used as cladding material. The rare earth oxide La2O3 was added to the 316 L stainless steel powder and the modification treatment was carried out. Laser cladding exper-iment was conducted on the surface of 1Cr18Ni9Ti stainless steel. The microstructure of the clad-ding layer was analyzed and the corrosion resistance was studied. The effect of rare earth content on the hardness of the cladding layer was analyzed. The effect of rare earth elements on laser cladding layer was studied.

A review on the effect of rare-earth elements on texture evolution during processing of magnesium alloys

Magnesium, the lightest structural metal, is approximately four times lighter than steel—the most widely used metal in industrial applications. Currently available Mg alloys, however, are impractically expensive for use in automotive structural components, as severe ductility problems require forming operations at elevated temperatures and an exclusion from critical safety components. With a strong impetus in research having sprung up during the last two decades, addition of rare-earth elements in small quantities emerged as a potential solution for simultaneously delivering the ductility and weight requirements for automotive applications. These improvements are arguably achieved by virtue of texture weakening and enhancement of non-basal slip. However, ways by which rare-earth elements modify texture remain very elusive, and no consensus on the driving mechanisms has been reached in the literature as of yet. We take a look back at different paradigms held for the action of rare-earth additions, and examine key facts that may reconcile controversies. We attempt to identify critical gaps and suggest venues to overcome them. These gaps, once filled, may promote Mg alloys to become a stronghold for lightweighting, which will exceptionally benefit our environment and wellbeing.

Effects of rare earth elements on the environment and human health: A literature review

REEs are a group of metals comprised of yttrium, fourteen lanthanide elements, and scandium, which have been called ‘industrial vitamins’ and a ‘treasury’ of novel materials due to their dominant role in technical progress and in the development of traditional industries. Despite the growing interest, information that has become available over the last two decades regarding RREs is relatively premature and scarce, which has led to the current controversy regarding the health benefits vs toxic effects of these materials. There are many environmental and health issues associated the production, processing, and utilization of REEs. This review offers an examination of the roles of REEs in the onset of cellular oxidative stress in reference to the impact of REE exposure to cells, animals, and plants, in order to explain disease and occupational poisoning of local residents, water pollution, and farmland destruction. Conversely, a body of evidence has shown REE-associated antioxidant effects in the treatment of many diseases. The content herein is aimed at presenting the recent and pending developments in the field of REE with respect to environmental and human health implications. Multi-faceted updates on the roles of REEs focusing on different organisms and exposure routes, and several issues regarding environmental and biological research, are discussed. The current gaps in information raise a number of open questions that deserve ad hoc investigation.

The effect of rare earth elements on phosphorus leaching in intact soil columns

The effect of rare earth elements on phosphorus leaching in intact soil columns

Effects of rare earth elements doping on ordered structures and ductility improvement of Fe–6.5 wt%Si alloy

Fe–6.5wt%Si alloy's poor ductility is mainly caused by the large amount of brittle ordered structure, and the significant reduction of Fe–6.5wt%Si alloy's order degree was found by rare earth elements (yttrium, lanthanum, cerium) doping, hence the average room temperature bending deflection increases to 0.77mm from 0.62mm and the average tensile elongation to failure at 400°C increases to 23.0% from 7.3% by 0.021wt% cerium doping. The order degree reduction phenomenon was manifested by the obvious decrease of B2 and D03 ordered structure reflection intensity in X-ray diffraction and selected area electron diffraction patterns and the ordered domains refinement in transmission electron microscopy. The rearrangement capability of adjacent atoms during order–disorder transformations is lowered due to the iron and silicon atoms are dragged by rare earth atoms, hence the formation of ordered phases is hindered, which provides a novel order degree reduction mechanism of Fe–6.5wt%Si alloy.

Study on the mutual effect of La and Gd on microstructure and mechanical properties of Mg-Al-Zn extruded alloy

The effects of rare earth elements (La, Gd) addition on the microstructure and the mechanical properties of as-extruded Mg-Al-Zn magnesium alloy under conditions of a medium temperature (230 °C) and a slow ram speed (0.1 mm/s) have been throughly investigated. The results show that the as-extruded bar presents smooth surface from the macroscopic view due to the fact that many non-basal <a> dislocations and few pyramidal 〈c + a〉 dislocations could be activated to enhance the formability in the extrusion process. A bimodal grain structure composed of fine dynamic recrystallized (DRXed) grains with globular Mg17Al12 precipitates located at grain boundaries and non-recrystallized (non-DRXed) coarse grains with thin continuous precipitation laths inside is generated in the alloy. More dislocation pile-ups and subgrain boundaries are exhibited in the DRXed region which shows a typical texture of extruded alloys containing rare earth elements. The modified extruded alloy shows much higher strength than that of as-extruded AZ80 under either tension or compression condition owing to grain refinement strengthening, precipitation strengthening, solid-solution strengthening, dislocation strengthening and subgrain strengthening. The finer DRXed grain size and the fine precipitates in the modified extruded alloy bring about its lower yield anisotropy. In addition, large and fragile Al2Gd and Al8Mn4Gd phases mainly give rise to the decrease in ductility of the modified extruded alloy.

Synthesis of high-stability acidic Ce3 + (La3 + or Sm3 +)~β/Al-MCM-41 and the catalytic performance for the esterification of oleic acid

Ce3+ (La3+ or Sm3+)~β/Al-MCM-41 molecular sieves were synthesized by impregnation and used to catalyze the esterification of oleic acid with short chain alcohols, such as methanol, ethanol, isopropanol, and isobutanol, to obtain biodiesel. Ce3+(La3+ or Sm3+)~β/Al-MCM-41 was found to exhibit excellent catalytic activity and stability. The effect of rare earth elements on the acidity of catalysts was examined in detail by NH3-TPD and Py-FTIR. The optimum conditions for the esterification of oleic acid with methanol were determined. Moreover, the kinetics of the esterification showed that the average reaction order (n) was 1.92, with an activation energy of 51.46kJ/mol.

Effects of Cerium and Lanthanum on the Corrosion Behavior of Al-3.0 wt.%Mg Alloy

Effects of rare earth elements (RE: cerium and lanthanum) on the corrosion behavior of Al-3.0 wt.%Mg alloy were investigated by electrochemical measurement and immersion test in 3.5 wt.% NaCl solution. The results indicated that a proper amount of rare earth (about 0.2 wt.%) could improve the corrosion resistance of Al-3.0 wt.%Mg alloy effectively, whereas that excessive rare earth addition would increase the corrosion rate and reduce the corrosion resistance. The corrosion behavior of Al-3.0 wt.%Mg alloys in 3.5 wt.% NaCl solution showed typical characteristics of pitting corrosion at the position of second phases. The more and the bigger the second phases, the more and the larger the pitting holes.

Promotional effects of rare earth elements (Sc, Y, Ce, and Pr) on NiMgAl catalysts for dry reforming of methane

The promoting effects of rare earth elements on NiMgAl catalysts for dry reforming of methane were clarified.

Al-Si-Re Alloys Cast by the Rapid Solidification Process / Stopy Al-Si-Re Odlewane Metodą Rapid Solidification

The aim of the studies described in this article was to present the effect of rare earth elements on aluminium alloys produced by an unconventional casting technique. The article gives characteristics of the thin strip of Al-Si-RE alloy produced by Rapid Solidification (RS). The effect of rare earth elements on structure refinement, i.e. on the size of near-eutectic crystallites in an aluminium-silicon alloy, was discussed. To determine the size of crystallites, the Scherrer X-ray diffraction method was used. The results presented capture relationships showing the effect of variable casting parameters and chemical composition on microstructure of the examined alloys. Rapid Solidification applied to Al-Si alloys with the addition of mischmetal (Ce, La, Ne, Pr) refines their structure.

Preparation and corrosion resistance of rare earth–silane composite conversion coatings on magnesium–lithium alloy surface

The poor corrosion resistance of magnesium–lithium alloy surface works against its application in aerospace, automobile, electronics, etc. In this research, some kinds of non-toxic and non-polluting rare earth and silane (RE–Si) composite conversion coatings were built up on Mg–Li alloy surface, and formation process of coatings was investigated. The parameters for coating preparation were determined, including immersion time and temperature, pH value of conversion solution and curing time. The optimized technological parameters for preparation of RE–Si composite coating were finally confirmed. The influence of doping nanoparticles on RE–Si composite coating was also discussed, and the microstructure of coatings shows that the addition of nanoparticles can effectively improve the compactness and uniformity of composite coating. The corrosion resistance of specimens with RE–Si composite conversion coating is improved to a great extent compared with those of substrate or specimens with single rare earth (RE) conversion coating or with silane coating. The result also indicates that corrosion resistance of RE–Si composite coating doping with nanoparticles is further improved. Composition of the composite coatings was analyzed, and the effect of RE elements and silane on coating formation process was investigated. Corrosion resistance mechanism of composite coatings on Mg–Li alloy surface was discussed.

Application of rare-earth element Y in refining impure copper

The effects of rare-earth element Y in refining impure copper were investigated in this paper. The composition, microstructures, and corrosion resistance properties of impure copper before and after refinement with Y were investigated using direct-reading spectrometry, inductively coupled plasma atomic emission spectrometry, optical microscopy, scanning electron microscopy, and potentiodynamic polarization measurements. The results show that the concentrations of impurities S, As, Sb, Bi, Al, Cd, and Se are remarkably decreased. Adding an appropriate amount of Y refines the microstructure and enhances the corrosion resistance properties of impure copper in HCl solution via a purification effect. The formation enthalpies of compounds formed between Y and various impurity elements were calculated on the basis of Miedema’s theory. The thermodynamic mechanisms of the refinement of impure copper by Y were also discussed

Quantification of the strengthening effect of rare earth elements during hot deformation of Mg-Gd-Y-Zr magnesium alloy

The flow stress of Mg-Gd-Y-Zr, Mg-Al-Zn, and Mg-Zn-Zr magnesium alloys during hot deformation were correlated to the Zener–Hollomon parameter through analyses based on the proposed physically-based and apparent approaches. It was demonstrated that the theoretical exponent of 5 and the lattice self-diffusion activation energy of magnesium (135kJ/mol) can be set in the hyperbolic sine law to describe the peak flow stresses. As a result, the influence of rare earth elements, gadolinium (Gd) and yttrium (Y), upon the hot working behavior was readily characterized by the proposed approach, which was not possible by the conventional apparent approach. It was shown quantitatively that the rare earth addition exerts a profound effect on the hot strength and hence on the creep resistance.

Serum Proteomic Analysis Based on iTRAQ in Miners Exposed to Soil Containing Rare Earth Elements.

To explore the toxic effects of rare earth elements (REEs) accumulated in human body, adopting the inductively coupled plasma mass spectrometry (ICP-MS) method, the present study measured REEs and the contents of eight other elements (Ca, Fe, Cu, Na, K, Zn, Mg, and P) in the hair of eight persons exposed to soil containing REEs for a long time as well as in the control group. In addition, proteomic analysis of serum of the two groups was conducted by isobaric tags for relative and absolute quantitation (iTRAQ) technique. Experimental results show that in the hair of the two groups, 15 REEs and eight other elements were detected, in which the content of La, Ce, Pr, Nd, Tb, Ho, Tm, Yb, and Fe in the exposure group is significantly higher than that of the control group, but the content of Ca in the exposure group is significantly lower than that of the control group; analysis yields out 29 differentially expressed proteins, in which 16 proteins are upregulated and 13 proteins are downregulated. Bioinformatics analysis of differentially expressed proteins demonstrates that they participate in various biological processes and five Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, forming an interaction network. Besides, some differentially expressed proteins may be related to neurovirulence, hepatotoxicity, pathological fibrosis, osteoporosis, and anticoagulation caused by REEs. The present experiment investigated the toxic effects of REEs accumulated in human body at the molecular level, which may lay a foundation for the future research of biological effect, threshold limit values, protection from exposure, and reasonable application of REEs.

First-principles calculations of structural stability and elastic properties of REB12 strengthening phases in boriding Mg–RE alloys

The effect of rare-earth elements (REs) on formation and elastic properties of strengthening precipitates in boriding Mg–RE alloys was determined by first-principles calculations. The preferential formation of a B12-cluster during boriding process results in the appearance of the only REB12 strengthening phases. The REB12 compounds possess the high hardness, which is mainly associated with the strong covalent bondings of B12-cluster. The RE types hardly affect the hardness of REB12 compounds, which is partially elucidated owing to a low fraction of RE–B metallic bondings.