Effect Of Rare Earth Metals Research Articles

Effect of yttrium on catalytic performance of Y-doped TiO2 catalysts for propane dehydrogenation

Defective bulk catalysts based on TiO2 have superior catalytic performance for propane dehydrogenation (PDH). The oxygen vacancy concentration and the number of active sites on the catalyst surface can be effectively tuned by doping metal in TiO2. Herein, yttrium (Y)-doped titanium dioxide (nY/TiOx) catalysts were in-situ synthesized via the coprecipitation method to study the effect of rare earth metal Y doping on the structure of TiO2 and the catalytic performance for PDH. Experimental results demonstrate that Y-doped TiO2 exhibits higher catalytic activity, propylene selectivity and stability than bare TiO2. Full characterizations with X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy of pyridine adsorption (Py-IR), temperature-programmed desorption of ammonia (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), and Raman techniques on these catalysts reveal that Y3+ can enter TiO2 lattice, and the lattice stability of the catalyst can be enhanced by replacing Ti4+ to form Y–O–Ti structure. Meanwhile, the introduction of an appropriate amount of Y can obviously promote the PDH reaction by adjusting the acidity of the catalyst, improving the release capacity of TiO2 lattice oxygen and increasing the formation of active centers. Nevertheless, excessive Y doping will lead to pore clogging, and the exposure of active sites will be reduced, resulting in the degradation of catalytic performance.

Effects of rare earth metals on microstructure, mechanical properties, and pitting corrosion of 27% Cr hyper duplex stainless steel

Abstract This research focuses on the addition of low-cost rare earth metals (REMs) to improve the comprehensive properties of hyper duplex stainless steels (DSSs). The effects of REM on the microstructure, mechanical properties, and pitting corrosion of hyper DSSs were analyzed by optical/scanning electron microscope metallographic examination, X-ray diffraction analysis, tensile test, impact test, and potentiodynamic polarization test. With the addition of REM, micro/nanoscale REM inclusions were formed, and the microstructure of the alloy was refined. With the increasing content of REM, the average diameter and area of inclusions in the alloy decreased at first and then increased. While the mechanical properties showed a trend of first increasing and then decreasing. An appropriate amount of stable REM inclusions could reduce the susceptibility of pitting corrosion and improve the pitting corrosion resistance of the alloy. The hyper DSSs with REM content in the range of 0.018–0.031 wt% have excellent mechanical properties and pitting resistance.

Effect of rare-earth metals on the hot strength of HSLA steels

Abstract An experimental study was done on the effect of rare-earth metals on a high-strength low-alloy steel. The work was focused in deriving the influence on Ce and La on the hot-working behavior. For this purpose, uniaxial hot-compression tests were carried out in a wide range of temperatures and strain rates. The effect of the rare-earth metals was determined by comparison of the characteristic parameters, describing the constitutive equations of the high-temperature response of the steel with, and without, rare-earth metals. The results showed that rare-earth metals were playing a major significant role on hardening mechanisms rather than on softening by dynamic recovery. On the contrary, rare-earth metals were able to delay the onset of dynamic recrystallization. All the present experimental results suggested that the latter roles are played by solid solution strengthening, through a solute drag effect, and not by precipitated particles.

Effect of Rare-Earth Metals on Density of Co–Fe–Si–B–Nb Alloy in Crystalline and Liquid States

Effect of Rare-Earth Metals on Density of Co–Fe–Si–B–Nb Alloy in Crystalline and Liquid States

The Effect of Rare Earth Metals Alloying on the Internal Quality of Industrially Produced Heavy Steel Forgings.

The paper presented the findings obtained by industrial research and experimental development on the use of rare earth metals (REMs) in the production of heavy steel ingots and their impact on the internal quality of the 42CrMo4 grade steel forging. REMs alloying was carried out after vacuuming the steel. A relatively large melting loss of cerium (about 50%) and its further decrease in casting due to reoxidation were observed. Refinement of structure and better mechanical properties of forged bar containing about 0.02 wt.% of Ce compared to that of the standard production were not achieved. The wind power shaft with content of about 0.06 wt.% of Ce showed high amount of REM inclusions, which were locally chained, and in some cases, initiated cracks. Four stoichiometrically different types of REM inclusions were detected in forgings, namely (La-Ce)2O2S + (La-Ce)O2 + SiO2 (minority); oxygen, phosphorus, arsenic, and antimony bound to lanthanum and cerium probably bonded with iron oxides La + Ce, MgO, Al2O3 a SiO2; (La-Ce)2O2S, FeO, SiO2, and CaO or CaS.

Natural Iron Ore as Oxygen Carrier Modified with Rare Earth Metal for Chemical Looping Hydrogen Production

Chemical looping hydrogen production (CLHG) represents a novel technology for H2 production. Natural iron ore is a potential oxygen carrier for CLHG but is facing a challenge of low deep reduction reactivity. This paper aims at promoting the reduction reactivity of iron ore and H2 production using Ce-doped and La-doped iron ore with an impregnation method. The oxygen carriers were characterized by SEM-EDX, XRD, and XPS. The reactivity and stability of the doped iron ore were evaluated in TGA. The CLHG process was carried out in a fixed bed system, and the effect of rare earth metal on oxygen carrier conversion and H2 production was evaluated. The results indicate that both Ce-doped and La-doped iron ore as oxygen carriers exhibited a higher reduction reactivity than the raw iron ore and a relatively stable redox performance at 900 °C after the initial activation process. Reasonable Ce loading (5–10%), La loading (2.5–15%), and temperature (above 850 °C) could promote oxygen carrier conversion and enhance H2 production. The La-Fe interaction enabled the iron ore to be oxidized to LaFeO3 (Fe3+) during water splitting, promoting H2 production. Carbon deposition was not formed during the reduction process, and H2 purity remained at 100% during the whole water splitting process.

Effect of Rare Earth Metals (Ce and La) Addition on the Performance of Al-Si-Cu-Mg Cast Alloys

Effect of Rare Earth Metals (Ce and La) Addition on the Performance of Al-Si-Cu-Mg Cast Alloys

Effect of Rare Earth Metals (Y, La) and Refractory Metals (Mo, Ta, Re) to Improve the Mechanical Properties of W-Ni-Fe Alloy-A Review.

Tungsten heavy alloys are two-phase metal matrix composites that include W–Ni–Fe and W–Ni–Cu. The significant feature of these alloys is their ability to acquire both strength and ductility. In order to improve the mechanical properties of the basic alloy and to limit or avoid the need for post-processing techniques, other elements are doped with the alloy and performance studies are carried out. This work focuses on the developments through the years in improving the performance of the classical tungsten heavy alloy of W–Ni–Fe through doping of other elements. The influence of the percentage addition of rare earth elements of yttrium, lanthanum, and their oxides and refractory metals such as rhenium, tantalum, and molybdenum on the mechanical properties of the heavy alloy is critically analyzed. Based on the microstructural and property evaluation, the effects of adding the elements at various proportions are discussed. The addition of molybdenum and rhenium to the heavy alloy gives good strength and ductility. The oxides of yttrium, when added in a small quantity, help to reduce the tungsten’s grain size and obtain good tensile and compressive strengths at high temperatures.

Fe-25%Cr-22%Ni-0.03%P 完全オーステナイト系ステンレス鋼の凝固割れ感受性に及ぼす希土類元素の影響

Fe-25%Cr-22%Ni-0.03%P 完全オーステナイト系ステンレス鋼の凝固割れ感受性に及ぼす希土類元素の影響

Metal cold resistance of the low-alloy steels welding joint, micro-alloyed REM

ABSTRACT The effect of rare earth metals (REM), introduced into the electrode coating, on the mechanical properties, chemical composition and impact toughness at test temperatures from +20 to −70°C deposited metal and metal of welding joint on steel 10ХSND was studied. The components of fracture under impact tests are determined: the work of crack initiation (KST3) and work of fracture (KSTr). The character of the fracture surface of the damaged samples is studied. There is an increase in the impact toughness of a metal, micro-alloyed REM, in the investigated temperature range of the tests.

Effects of Rare-Earth Metals on the Thermal Stability and Glass-Forming Ability of Al–Ni–Co–R Amorphous Alloys

Al86Ni4Co4R6 and Al86Ni6Co2R6 (R = Nd, Sm, Gd, Tb, or Yb) metallic ribbons were produced by planar flow spin casting. The glass-transition and phase-transformation temperatures of these alloys were determined in crystallization kinetic studies. Glass-forming criteria for these alloys were calculated from differential scanning calorimetry (DSC) and differential thermal analysis (DTA) data. The rare-earth metals and combinations of transition metals useful to enhance the thermal stability and glass-forming ability of the alloys were found.

Coherent toxicity prediction framework for deciphering the joint effects of rare earth metals (La and Ce) under varied levels of calcium and NTA

With the development of modern technologies, the exploitation and application of rare earth metals (REMs) have increased parallelly. Consequently, more REMs are entering into the environment and therefore there is a pressing need to assess their potential environmental hazards. Here, a standard toxicity test with wheat (Triticum aestivum) was conducted to investigate the single and mixture toxicity of La and Ce in solutions with different levels of calcium and nitrilotriacetic acid (NTA) and results were deciphered by different modeling approaches. Both La and Ce caused adverse effect to wheat, but the presence of Ca and NTA alleviated their toxicity. The obtained EC50 for [La] or [Ce] changed by more than 28-fold and by 4-fold, respectively, with the increase of Ca or NTA. The biotic ligand model (BLM) explained approximately 93% variation of single La or Ce toxicity. The binding constants obtained were 4.14, 6.67, and 6.59 for logKCaBL, logKLaBL, and logKCeBL respectively. The electrostatic toxicity model (ETM) was proved as effective as the BLM, with R2 = 0.93 for La and R2 = 0.92 for Ce. For La–Ce mixtures, parameters from single toxicity approaches were applied successfully to predict the mixture toxicity with concentration addition (CA) model based on the BLM or ETM theory (R2 = 0.92 and RMSE = 8.56; R2 = 0.90 and RMSE = 9.6, respectively). Thus, the results obtained in this study prove that both ETM and BLM theories are appropriate to predict single and mixture REMs toxicity, providing coherent and promising tools for the risk assessment of REM pollution.

Effect of Rare Earth Metal (RE = La, Pr, Nd, Y) Doping on Co–Ce Composite Oxide and Its Application in Catalytic Combustion of Chlorobenzene

Rare earth metal (RE = La, Pr, Nd, Y)-doped CoCeOx catalysts were prepared and evaluated for eliminating chlorobenzene (CB). Characterization results showed that the doped RE metal simultaneously a...

Биотехническая система оценки токсичности соединений редкоземельных металлов

Introduction. Expanding the scope of application of rare-earth metal compounds that are unique in their properties increases the interest of many researchers in studying the impact of rare-earth metals and their compounds on human health and the environment. One of the most relevant and modern methods for assessing the safety of the studied media for a biological test object is bioassay. Problem Statement. The objective necessity of determining the combined effect of rare earth metals and their compounds on human health and the environment involves the use of biological systems. Modern methods of bioassay are extremely sensitive, which is sufficient to determine sub-threshold concentrations of hazardous substances in accordance with international standards. Thus, the use of these methods can make it possible to determine the index and the degree of toxicity of rare earth metal compounds with high accuracy in order to prepare a package of necessary documentation on industrial safety of products. Theoretical Part. Based on the studied toxicological effects of rare earth metals, the authors proposed to conduct a toxicity assessment based on the concept of biotechnical systems. The object of research was oxides and carbonates of rare earth metals. The results of the study to determine the index and the degree of toxicity of rare earth metal compounds, as well as to assess the lethal concentration of LC50 (24 h) by biotesting using test organisms Paramecium Caudatum were used to write a safety data sheet for cerium oxide and carbonate. Conclusion. The studies have shown that a certain modification of the technical solutions embedded in the devices of the Biotester series makes it possible to correctly solve the problem of assessing the toxicity of rare earth metals and their compounds. Based on the research results, the safety data sheets were developed.

High-pressure diamond synthesis in the presence of rare-earth metals

Abstract The effect of rare-earth metals on diamond crystallization processes in the Mg-REM-C system (REM = Sc, Y, La, Pr, Nd, Dy, and Yb) was studied at 7.8 GPa and 1800 °C. It was found that the rare-earth metals added in an amount of 10 wt% had different effects on diamond crystallization. Sc, La, Pr, and Dy, only slightly affected the intensity of diamond synthesis as compared to the undoped Mg-C system. Yb, Y, and Nd significantly reduced the degree of conversion of graphite to diamond. The effect of higher contents of rare-earth metals on diamond crystallization was studied for the Mg-Pr-C system with a Pr content varied from 0 to 80 wt%. It was found that with increasing Pr content the degree of the graphite-to-diamond conversion decreased and at 80 wt% Pr diamond synthesis was terminated and mass crystallization of metastable graphite took place. The morphology of diamonds synthesized in the Mg-REM-C system was determined by the {1 0 0} faces. The surface microrelief of the faces was connected with crystal defectiveness and characterized by specific features, depending on the system composition and the degree of graphite-to-diamond conversion. From the spectroscopic characterization it was found that similarly to their action on diamond synthesis, different REM additives produced different effects on photoluminescence characteristics of the synthesized diamonds. Those rare-earth metals which only slightly affected diamond crystallization, showed no significant effects on the PL spectra relative to the undoped Mg-C system. Diamonds produced with Y, Nd and Yb additives showed a number of new photoluminescence features, which could be related to defects inhibiting diamond crystal growth.

Effect of Rare Earth Metals on the Mechanical Properties and Fractography of Al–Si-Based Alloys

The present study was performed on A356 and A413 alloys in non-modified and Sr-modified conditions. To these alloys, pure rare earth (RE) metals, mainly lanthanum (La) and cerium (Ce), were added in the amount of 1 wt% each, individually or combined. The results showed that the addition of 2% RE leads to a significant reduction in the grain size (~ 60%) compared to the base alloy. However, it also leads to precipitation of a large amount of insoluble intermetallics (~ 10% in volume fraction). These intermetallics cause a significant decrease in the alloy ductility and hence deteriorate the tensile properties and impact energies. In addition, Sr may also cause destabilization of the RE intermetallics with possibility of partial dissolution during solution heat treatment. The RE metals have an affinity to react with Sr leading to partial demodification of the eutectic Si. They also react with Cu, diminishing the alloy response to age hardening. The RE intermetallics act as crack initiation sites, leading to premature failure of the sample. The combined occurrence of these various effects complicates the prediction of the alloy behavior.

Influence of rare earths alloying addition on the corrosion behavior of Zn in neutral aerated sodium chloride solution

The effect of rare earth metals (Gd, Dy, Er,) addition on the corrosion behavior of Zn has been investigated. The corrosion resistance of Zn99Gd1, Zn99Dy1, and Zn99Er1 (at%) alloys has been assessed by open circuit potential and electrochemical impedance spectroscopy (EIS) measurements carried out in a 0.1 M NaCl solution, at approximately neutral pH, without stirring and in contact with the air. For comparison, the electrochemical tests have also been carried out on unalloyed Zn. Moreover, the surface morphology and nature of the corrosion products have been investigated. The results indicated that rare earths addition significantly improves the corrosion behavior of unalloyed Zn. This improvement is most likely due to enhanced barrier properties of the corrosion products layer and additional active corrosion protection originated from the inhibiting action of the lanthanide ions entrapped as oxides/hydroxides in this surface layer.

Effect of Rare-Earth Metals on Cast High-Temperature and Corrosion-Resistant Alloy Cleanliness and Service Properties

It is shown that addition of rare earth metals to cast corrosion-resistant high-temperature alloys facilitates a reduction in harmful impurities (oxygen, nitrogen, sulphur) and substantially increases operating characteristics. The microstructure in cast condition and after complete heat treatment is typical of hightemperature nickel alloys. It is established that exceeding the optimum REM content leads to eutectic γ′-phase melting that may cause a reduction in operating properties. The introduction of waste, including substandard materials, during melting does not lead to a reduction in operating properties.

Effect of Rare Earth Metals on Mechanical and Corrosion Properties of Al-Zn-Mg-Cu-Zr Alloy

Abstract The effect of rare earth metals on mechanical and corrosion properties of 7085 aluminum alloy (Al-7.5Zn-1.5Mg-1.4Cu-0.15Zr) was investigated by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Intergranular, exfoliation corrosion, hardness, tensile test and electrical conductivity test were performed Al alloys on both with and without rare earth additives. Results show the Al alloys with rare earth metals present better mechanical properties such as higher strength and hardness as a result of finer microstructure in comparison with those without the additives. The corrosion resistance is greatly improved by adding rare earth metals. Intergranular corrosion resistance is enhanced from Level IV to Level II, the denudation level for 48 h is improved from EB to PA and ISSRT reflecting stress corrosion resistance was enhanced from 65% to 96%.

Effect of rare earth metal on plasma properties in GMAW using CO2 shielding gas

Gas metal arc welding (GMAW) process, the effect of welding polarity and rare earth metal (REM) elements on physical properties was investigated through the observation of the plasma characteristics using the optical emission spectroscopy method which is suitable respectively to the O plasma region and the Fe plasma region. At the present experimental conditions, the MG-50 wire electrode and KC-500 wire electrode (REM-added electrode) were used for welding with 100% CO2 shielding gas. The results of the KC-500 wire electrode with DCEN polarity showed that the maximum temperature of the O plasma region was around 13,000–13,500 K. The maximum occurs at the region apart from the arc axis. The effect REM elements can cause high current density and electromagnetic pinch force at the tip of electrode. Meanwhile, the metal droplet diameter became smaller like spray transfer during arc with DCEN polarity.