Effects Of Rare Earth Elements Research Articles

Effects of rare-earth elements on the oxidation behavior of γ-Ni in Ni-based single crystal superalloys: A first-principles study from a perspective of surface adsorption

The mechanism of rare-earth element (RE) effects on the oxidation resistance of Ni-based single crystal (SC) superalloys are investigated by studying the adsorption behaviors of an oxygen atom (O) on clean and RE-alloyed (RE = Ce, Dy, La) γ-Ni(100) and γ-Ni(111) surfaces via first-principles method. The results show that substituting a RE atom on the top layer of γ-Ni surface could stabilize the adsorption of O on γ-Ni surfaces, regardless of surface orientation. Detailed electronic structure analyses indicate that the increased chemical bonding strength between O and RE atoms is considered to be the main reason for this result. Furthermore, the adsorption energies of O on Ni(100) surface are further increased when a single RE atom substitutes at a subsurface layer site. The combined effects of RE-O interaction and local lattice distortion are responsible for this phenomenon. These results help to understanding the underlying mechanism for the oxidation resistances of Ni-based SC superalloys improved by a small amount of RE additions.

Tetrad effect of rare earth elements caused by fractional crystallization in high-silica granites: An example from central Tibet

Determining the formation mechanism (fractional crystallization vs. melt-fluid interaction) of the REE tetrad effect in high-silica granites is critical for understanding trace elemental behaviors (e.g., enrichment of rare metals) during magmatic and hydrothermal evolution. This study reports new petrography, zircon U-Pb ages, trace elemental and Hf isotopic, and whole-rock geochemical data of high-silica granites from the Gajin Batholith in the central Lhasa Terrane, Tibet. All samples are dated at ca. 100 Ma and likely formed during Lhasa-Qiangtang collision. These samples are syenogranites and alkali-feldspar granites, belonging to high-silica I-type granites (SiO2 = 74.2–78.2 wt%), having high total-alkalis, low magnesian, marked enrichments in Pb, U, Th, and Rb, and marked depletions in Ti, Eu, P, Sr, and Ba. The petrological and geochemical data indicate moderate (0–20%) fractionation of plagioclase + K-feldspar + biotite (5:3:2). The REE data clearly define regular chondrite-normalized patterns (No-tetrad Group) and pronounced tetrad patterns (Tetrad Group). The REE tread effect in Tetrad Group can be reproduced by fractionation of monazite and allanite as indicated by a Rayleigh fractionation modeling. New modeling results for samples reported elsewhere, along with petrographic observations and decoupling between the REE tetrad effect and fractionation of twin-elements, demonstrate that the REE tetrad effect in high-silica granites is inherited from fractional crystallization rather than formed by melt-fluid interaction as suggested widely.

High-temperature oxidation of Moss—Mo3Si alloys doped with Sc or Y in air and in a steam-air mixture

For continuation of investigations aimed at studying the effect of rare earth elements (RRE) on the behavior of metal-silicide molybdenum alloys in oxidizing environments, the results of experimental modeling of high-temperature oxidation of alloys based on Mo—15 (at.%) Si and doped with Sc or Y in the isothermal mode in the air and in a steam-air environment are presented. New data on the effect of REE on oxidation resistance of alloys of the Mo—Si system of hypoeutectic composition, the formation of scale on their surface, the phase composition and the structure of oxidation products was obtained.

Bi-directional regulation functions of lanthanum-substituted layered double hydroxide nanohybrid scaffolds via activating osteogenesis and inhibiting osteoclastogenesis for osteoporotic bone regeneration.

Rationale: Osteoporotic patients suffer symptoms of excessive osteoclastogenesis and impaired osteogenesis, resulting in a great challenge to treat osteoporosis-related bone defects. Based on the positive effect of rare earth elements on bone metabolism and bone regeneration, we try to prove the hypothesis that the La3+ dopants in lanthanum-substituted MgAl layered double hydroxide (La-LDH) nanohybrid scaffolds simultaneously activate osteogenesis and inhibit osteoclastogenesis.Methods: A freeze-drying technology was employed to construct La-LDH nanohybrid scaffolds. The in vitro osteogenic and anti-osteoclastogenic activities of La-LDH nanohybrid scaffolds were evaluated by using ovariectomized rat bone marrow stromal cells (rBMSCs-OVX) and bone marrow-derived macrophages (BMMs) as cell models. The in vivo bone regeneration ability of the scaffolds was investigated by using critical-size calvarial bone defect model of OVX rats.Results: La-LDH nanohybrid scaffolds exhibited three-dimensional macroporous structure, and La-LDH nanoplates arranged perpendicularly on chitosan organic matrix. The La3+ dopants in the scaffolds promote proliferation and osteogenic differentiation of rBMSCs-OVX by activating Wnt/β-catenin pathway, leading to high expression of ALP, Runx-2, COL-1 and OCN genes. Moreover, La-LDH scaffolds significantly suppressed RANKL-induced osteoclastogenesis by inhibiting NF-κB signaling pathway. As compared with the scaffolds without La3+ dopants, La-LDH scaffolds provided more favourable microenvironment to induce new bone in-growth along macroporous channels.Conclusion: La-LDH nanohybrid scaffolds possessed the bi-directional regulation functions on osteogenesis and osteoclastogenesis for osteoporotic bone regeneration. The modification of La3+ dopants in bone scaffolds provides a novel strategy for osteoporosis-related bone defect healing.

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.

High-Temperature Heat Capacity of Pb9R(GeO4)3(VO4)3 (R = La, Pr, Nd, Sm) Apatites

The apatite-like Pb9Pr(GeO4)3(VO4)3 and Pb9Sm(GeO4)3(VO4)3 compounds were prepared by solid-phase synthesis using oxides as starting chemicals: PbO, Pr2O3 (Sm2O3), GeO2, and V2O5. The successive annealing was carried out at 773–1073 K in the air. The effect of rare-earth elements on the structure of the Pb9R(GeO4)3(VO4)3 (R = La, Pr, Nd, Sm) apatites and basic thermodynamic functions was investigated. The temperature dependence (350–1050 K) of the heat capacity of the Pr(Sm)-containing apatites has been determined by differential scanning calorimetry. It has been established that the Cp = f(T) curve for the Pb9Pr(GeO4)3(VO4)3 compound has an extremum associated with a polymorphic transformation in the region of 978 K.

The influence of rare earth element lanthanum on the microstructures and properties of as-cast 8176 (Al-0.5Fe) aluminum alloy

The effects of rare earth element on the microstructures, tensile properties and electrical properties of aluminum alloys have brought about widespread interesting in the last few decades. However, contradictory results are usually reported, and there is little research concerning the effect law of trace lanthanum (the addition is below 0.1 wt%) on the as-cast microstructures, electrical conductivity and the tensile properties of 8176 aluminum alloy which is one of the most widely used aluminum conductor alloy. In this work, solidification experiments were performed with 8176 aluminum alloy and the effects of lanthanum addition was investigated. The results demonstrated that the lanthanum addition can promote the refinement of the alpha Al grains, the modification of Al13Fe4 intermetallic phase. The elongation and electrical conductivity simultaneously enhance with lanthanum addition when the additive amount is less than 0.08%, while the elongation decreases when the additive amount reaches to 0.1% due to the formation of intermetallic phase. The enhancement of the elongation is mainly ascribed to the modification of Al13Fe4 intermetallic phase, the enhancement of the electrical conductivity is attributed to the reduction of solid solubility of Si and Fe elements in Al matrix. These results indicate that the addition of micro-alloying element lanthanum is a prospective method for simultaneously elevating the electrical conductivity and tensile properties of the 8176 aluminum alloy.

Effects of rare earth elements (Ce, La) on microstructure and mechanical properties in compacted graphite iron

ABSTRACT Microstructure and mechanical properties of compacted graphite iron (CGI) alloyed with different additions of rare earth (RE) elements are analysed in this paper. Experimental results show that graphite presents mostly vermicular shape when the content of RE is less than 0.041%. The shape of graphite becomes spherical after more RE is added. Tensile strength is improved significantly with the increase of RE content at room temperature and 400°C. Growth rate of main crack decreases obviously after RE alloying during thermal fatigue tests at 600°C. RE elements tend to segregate towards the interface between graphite and matrix, which leads to the change of graphite morphology. Auger electron spectroscopy (AES) results also show that Ce atoms will concentrate towards fracture surface, thus improving the oxidation resistance of the fracture surface at high temperature and crack propagation is inhibited.

Association between exposure of light rare earth elements and outcomes of in vitro fertilization-embryo transfer in North China

The adverse health effects of rare earth elements (REEs) on reproductive health remain a subject of debate, and few clinical observations are available. This study investigated the association between light REEs (LREEs) exposure and the outcome of in vitro fertilization–embryo transfer (IVF-ET). We recruited a total of 305 women undergoing IVF-ET in Beijing City and Shandong Province of northern China. Their demographic information and lifestyle characteristics were collected using questionnaires at enrollment. Fasting blood samples were collected on the day before the IVF-ET treatment cycle began. Serum concentrations of the LREEs of concern were analyzed using inductively coupled plasma-mass spectrometry, and four LREEs were measured with a high detection rate, including lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd). We found that a higher serum La concentration was associated with a 30% increased likelihood of clinical pregnancy failure [relative risk (RR) = 1.30, 95% confidence interval (CI): 1.00–1.67] and a 230% increased likelihood of preclinical spontaneous abortion (RR = 3.30, 95% CI: 1.57–6.94). There was a negative correlation between serum La concentration and the number of good-quality oocytes. For the other LREEs, no statistically significant associations were observed. We concluded that a high serum La concentration may have an adverse effect on IVF-ET outcomes.

The effect of rare earth element (Er, Yb) doping and heat treatment on suspension stability of Y2O3 nanoparticles elaborated by sol-gel method

Sol–gel processing was used to fabricate undoped and rare-earth (Er, Yb) doped very fine Y2O3 nanoparticles under supercritical drying conditions of ethanol using an autoclave and annealed at 500 °C and 800 °C for 2 h. The Er and/or Yb concentration is fixed at 5 mol % for doped and co-doped nanoparticles. The as-synthesized Y2O3 nanopowder was characterized by the X-ray diffraction, scanning electron microscopy and thermogravimetric analysis (TGA) coupled with differential thermal calorimetry (DTA). The effects of solvent, heat treatment and the doping on the suspension stability of yttrium oxide (Y2O3) nanoparticles doped rare-earth elements (Er and Yb) were evaluated by UV-Visible spectroscopy, zeta potential measurement and particle size in suspension, thus, Hamaker 2 software. During this work, the particle analysis showed that the resulting nanoparticles had a pure cubic structure and nano-sized crystallites of about 8–38 nm. The heat treatment of the nanopowders causes a rapid decantation of the suspensions and the Er doped nanoparticles suspension had a good stability.

Rare earth elements in umbilical cord and risk for orofacial clefts

Questions remain about the effects of rare earth elements (REEs) on reproductive health, and no study has explored in utero exposure to REEs and risk of orofacial clefts (OFCs). We recruited subjects from a case-control study conducted in Shanxi Province, China. Concentrations of fifteen REEs were quantified in umbilical cord samples by means of Inductively Coupled Plasma Mass Spectrometry measurements. We employed logistic regression and weighted quantile sum (WQS) regression models to estimate the association between REEs exposures and OFCs. Of 226 subjects included in our study, 34 were cleft lip only, 44 were cleft lip with cleft palate and 6 were cleft palate only. In the logistic regression model, concentrations above the median of all subjects were associated with an increased OFCs risk of 2.35-fold (95% CI: 1.22, 4.53) for Lanthanum and 2.12-fold for Neodymium (95% CI: 1.10, 4.10) adjusting for maternal age, BMI, gestational weeks, sex of infants and passive smoking. In WQS model, a quartile increase in the index resulting in an increase of 3.10 (95% CI: 1.38, 6.96) in the odds of OFC. Lanthanum and Neodymium were suggested to be important factors. The results were largely consistent for OFC subtypes. In conclusion, in utero exposure to mixtures of REEs increased the risk of OFCs. Lanthanum and Neodymium were likely to be important factors in the development of OFCs.

SYNTHESIS AND CHARACTERIZATION OF RARE EARTH SUBSTITUTED M -TYPE (Sr-Ba) HEXAFERRITES

Effect of Rare earth elements (PrMn) substitution on the structural of Electrical and Dielectric properties Sr0.5-x Ba0.5PrxMnyFe12-yO19 (x =0.00–0.10; y =0.00–1.00) Hexaferrites prepared by sol–gel auto combustion is reported. The synthesized samples were characterized by Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), AC and DC analysis. The XRD analysis confirmed the formation of single and double phase M-type Hexa-ferrite structures. The lattice parameters were found to be increasing as Rare earth (PrMn) contents were increasing, which is attributed to the ionic sizes of the implicated cations. The rare earth (PrMn) seems to be entirely soluble in the lattice. SEM revealed that the grain size decreased with increasing rare earth (PrMn) substitution. The coercivity values (780– 1077cm-1 ) of all sample lies in the range of M-type hexa-ferrite’s, which indicated that an increase of anisotropy was achieved by substitution of rare earth doping, while the size of particles drastically reduced from 10 to 1 µm. The increased anisotropy and fine particle size is useful for many applications such as improving signal noise ratio of recording devices.

Effect of Rare-Earth Elements and Heat Treatment on the Structure and Properties of a Heat-Resistant Cast Mg–REM–Zr Magnesium Alloy

Experimental compositions of a new heat-resistant cast magnesium alloy are considered, the compositions are corrected, and the optimum compositions of the new cast magnesium alloy with rare-earth metals (REMs) are selected for durability tests at a high temperature. Heat treatment conditions are corrected. The structure and mechanical properties of the cast Mg–REM–Zr magnesium alloy are studied. Tests of the mechanical properties of individually cast samples and the samples cut from an experimental casting (aggregate cover) are performed at room and elevated temperatures.

The effect of rare earth elements on the work softening behavior of as-cast Mg-4Al-2Sn

This work explores the addition of 1% Rear Earth (RE) elements on the Mg–4Al–2Sn magnesium alloy, with an emphasis laid on the microstructural evolution during solidification and subsequent hot deformation behavior. The morphology of the α-Mg dendrites changes from the butterfly-like (growth at the non-basal planes) to the snow-flake like (growth at the basal planes) due to the addition of RE elements. Dendrite morphology transition (orientation transition) lead to the formation of the various macro-texture at the solidification interval. Subsequently, an appropriate correlation was established between the dendrite orientation selection, solidification texture and deformation behavior of the as-cast microstructure. The workability increases due to the addition of RE elements, which is related to the initial solidification texture and the morphology of the α-Mg dendrites. The results indicated that the dendrites which have snow-flake like morphology in the RE bearing alloys was more favorable for breaking of as-cast microstructure and occurrence of dynamic recrystallization.

Effect of rare earth elements (La, Y, Pr) in multi-element composite perovskite oxide supports for ammonia synthesis

A series of BaCeO3 modified with different rare earth elements (La, Y, Pr) were synthesized by co-precipitation and calcination and the effect of rare earth elements for catalytic ammonia synthesis under mild conditions was studied. The ammonia synthesis performance tests show that 2.5% Ru/BaCe0.9La0.1O3–δ catalyst (All the percentages of Ru in this article are in mass fraction) exhibits the highest ammonia synthesis rate (34 mmol/(g·h)) at 3 MPa, 450 °C, and no sign of deactivation after 100 h of reaction. H2-TPR and XPS analyses indicate that the introduction of La increases the amount of oxygen vacancies of the catalyst, which is beneficial to increasing the electron density of Ru surface. HRTEM analysis shows that the Ru particle size is reduced greatly after La is introduced, which facilitates the catalyst generating more B5-type sites (active sites of Ru species for NN dissociation). CO2-TPD analysis indicates that BaCe0.9La0.1O3–δ has stronger basicity, which promotes electrons transfer from support to Ru. This work provides an effective method for design and synthesis of Ru-based multi-element composite perovskite oxide catalysts.

Effects of rare earth elements on the microstructure and wear properties of TiB2 reinforced aluminum matrix composite coatings: Experiments and first principles calculations

In this work, effects of rare earth elements on microstructure evolution and wear properties of TiB2 reinforced aluminum matrix composite coatings were investigated by the combination of first principles calculations and experimental investigation. The calculated results revealed that Sc exhibited the most effective modification ability due to the most negative adsorption energy and the largest charge transfer compared with La and Y. Based on the calculated results, the rare earth elements modified composite coatings were synthesized by laser processing. The as-obtained composites were characterized by back-scattered electron imaging (BSE) and spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM). Results indicated that the addition of Sc can greatly refine the particle size of TiB2, improve the distribution of particles and lead to the morphology transforming from hexagonal disk to sphere. As a result, the microhardness and wear properties of the composite coatings were enhanced significantly. The best properties were achieved in the composite with 0.6 wt% Sc addition, which exhibited highest microhardness of 920 HV, lowest friction coefficient of 0.4 and wear rate of 24.8 mg /h. The preferential adsorption of rare earth elements on TiB2 facets is proposed to be the main modification mechanism which results in the morphology evolution and wear properties improvement.

Comparative study of mechanical, corrosion and erosion—corrosion properties of cast hyper-duplex and super-duplex stainless steels

Duplex stainless steels (DSSs) used in subsea structures and desalination industries require high corrosion and erosion resistance as well as excellent mechanical properties. The newly introduced cast duplex grade ASTM A890 7A has a unique composition and is expected to have a much better resistance to corrosion and erosion compared with the super-duplex grades 5A and 6A. This work is a comparative study of the mechanical properties, corrosion, and erosion-corrosion resistance of super-duplex grades 5A and 6A and the hyper-duplex grade 7A. The three DSSs exhibited equiaxial austenite islands in the ferrite matrix and balanced phase ratios. The hardness of the grade 7A was nearly 15% higher than those of the super-duplex grades, which is attributed to the effect of the higher contents of W and Mn in 7A. The impact toughness of grade 7A was found to be lower than those of the super-duplex grades due to the carbide precipitation resulting from the partial substitution of Mo with W. The oxide layer strengthening effect of rare earth elements and the higher pitting resistance equivalent number (PREN) of grade 7A resulted in higher corrosion resistance. The harder and more passive grade 7A showed a 35% lower material loss during erosion-corrosion.

The Effect of Rare-Earth Element on the Optical and Structural Properties of SnO2

The Effect of Rare-Earth Element on the Optical and Structural Properties of SnO2

Recrystallization texture development in rare-earth (RE)-doped non-oriented silicon steel

High-grade non-oriented silicon steel with higher permeability and lower core loss has become the pursed target with the rapid development of electrical machines. The effects of rare-earth (RE) element on recrystallization texture in RE-doped Fe-3.1 wt.% Si-1.2 wt.% Al non-oriented silicon steel were investigated by macro- and micro-texture analyses. Nonlinear variation of recrystallization texture with RE element content was observed. In the competition among main recrystallization texture components, favorable {113} and λ fiber ( //ND) are strengthened and unfavorable γ fiber is evidently decreased by the addition of RE element, whereas the effect of RE element is reversed by excess RE element. The recrystallization texture development is determined by RE-affected nucleation and grain growth in terms of grain boundary migration related to segregation and inclusion. The properly inhibited grain boundary mobility can promote favorable recrystallization texture by the improved nucleation and efficient grain growth.

Effects of Rare Earth elements on microstructure evolution and mechanical properties of 718H pre-hardened mold steel

718H Pre-hardened mold steels with different Rare Earth (RE) contents were prepared to investigate the influence of RE on microstructure evolution and mechanical properties through a series of experiments and theoretical analysis. The results indicated that the toal oxygen (T.O) content decreased from 15 ppm to 6 ppm with 0.022 wt% RE addition, which is attributed to the active chemical properties of RE elements. For test steels, RE additions of 0.012 wt% and 0.022 wt% were significantly effective for refining inclusions by eliminating 11.5% large-sized inclusions with diameter exceeding 10 μm compared with that of 0RE steel. RE addition contributed to modify irregular MnS and Al2O3 inclusions into ellipsoidal RE-inclusions (RE2O3, RES, RE2O2S and REAlO3). The purification of molten steel and the modification of inclusions by RE treatment have significant effects on improvement of the fatigue crack growth tests (FCG) inhibition ability and impact energy as well as the isotropy. However, excessive addition of RE elements (0.07 wt%) seriously reduced the impact energy, ultimate tensile strength and FCG inhibition ability due to rapidly increase of the volume fraction of large-sized inclusions. In addition to the inclusions formed by RE treatment, trace solid solution RE atoms improve the stability of undercooled austenite, resulting in the transformation region of bainite and perlite of 0.07RE steel shifting to the bottom right and prolonging the incubation period compared with that of 0RE steel.