Effect Of Rare Earth Metals Research Articles

Effect of Rare Earth Metals on Porosity Formation in A356 Alloy

The present study was performed on A356 alloy containing various amounts of La, Ce or La + Ce, without and with about 80–100 ppm Sr. The main objective was to evaluate the porosity formed in rare earth metals (RE) containing Al–Si cast alloys. The results reveal that the addition of large amounts of RE (approximately 3%) would cause a marked increase in the freezing zone coupled with a marked volume fraction of RE-based intermetallics which would reduce the alloy feedability, leading to the formation of a significant percentage of shrinkage porosity. This situation is more severe in Sr-treated alloys. The depression in the eutectic Si temperature is not necessarily a parameter to consider in determining the degree of eutectic modification. Cerium is relatively more effective than La in terms of porosity formation.

Are we underrating rare earths as an electrocatalyst? The effect of their substitution in palladium nanoparticles enhances the activity towards ethanol oxidation reaction

The promotional effects of rare earth metals are exploited in enhancing the activity and stability of Pd towards the ethanol oxidation reaction both experimentally and theoretically.

Effect of Rare Earth Metals, Sr, and Ti Addition on the Microstructural Characterization of A413.1 Alloy

The present work was performed on A413.1 alloy containing 0.2–1.5 wt% rare earth metals (lanthanum or cerium), 0.05–0.15% Ti, and 0–0.02 wt% Sr. These elements were either added individually or combined. Thermal analysis, image analysis, and electron probe microanalysis were the main techniques employed in the present study. The results show that the use of the depression in the eutectic temperature as a function of alloy modification cannot be applied in the case when the alloy is treated with rare earth metals. Increasing the concentration of RE increases the solidification zone especially in Sr-modified alloys leading to poor feeding ability. This observation is more prominent in the case of Ce addition. Depending upon the amount of added Ti, two RE based intermetallics can be formed: (i) a white phase, mainly platelet-like (approximately 2.5 μm thick), that is rich in RE, Si, Cu, and Al and (ii) a second phase made up of mainly grey sludge particles (star-like) branching in different directions. The grey phase is rich in Ti with some RE (almost 20% of that in the white phase) with traces of Si and Cu. There is a strong interaction between RE and Sr leading to a reduction in the efficiency of Sr as a eutectic Si modifier causing particle demodification.

Influence of rare earth metals on structure and performance of Ni2P/MCM-41 hydrodesulfurisation catalysts

A series of rare-earth-modified M-Ni2P/MCM-41 (M=Pr, Nd, Ce, La, Y) catalysts has been prepared by means of a temperature-programmed reduction method. The prepared catalysts were characterised by X-ray diffraction, N2-adsorption specific surface area measurements, X-ray photoelectron spectroscopy and CO uptake. The effects of rare earth metals on catalyst activity for hydrodesulfurisation (HDS) of dibenzothiophene (DBT) were studied. The results showed that the addition of rare earth metals increases the surface area and pore volume of the catalysts. Rare earth metals can promote formation of the Ni2P phase and induce a better Ni2P dispersion but they do not change the mechanism of HDS of DBT. Pr-Ni2P/MCM-41 exhibited the highest HDS activity. At reaction temperature of 300 °C, pressure of 3.0 MPa, hydrogen/oil volume ratio of 500, and weight hourly space velocity(WHSV) of 6.0 h−1, the addition of Pr increased the conversion of HDS of DBT by 16.7%.

Effect of Rare Earth Metals on the Microstructure of Al-Si Based Alloys.

The present study was performed on A356 alloy [Al-7 wt %Si 0.0.35 wt %Mg]. To that La and Ce were added individually or combined up to 1.5 wt % each. The results show that these rare earth elements affect only the alloy melting temperature with no marked change in the temperature of Al-Si eutectic precipitation. Additionally, rare earth metals have no modification effect up to 1.5 wt %. In addition, La and Ce tend to react with Sr leading to modification degradation. In order to achieve noticeable modification of eutectic Si particles, the concentration of rare earth metals should exceed 1.5 wt %, which simultaneously results in the precipitation of a fairly large volume fraction of insoluble intermetallics. The precipitation of these complex intermetallics is expected to have a negative effect on the alloy performance.

Effect of Lanthanum Addition on Fluidity of Complex Al-11Si-Cu-Mg Cast Alloy

This research was to determine the effect of rare earth metal (REM) on the fluidity of eutectic Al-11Si-Cu-Mg cast alloy. The rare earth metal used here is Lanthanum to produce Al-11Si-Cu-Mg-0.1La, Al-11Si-Cu-Mg-0.5La and Al-11Si-Cu-Mg-1.0La alloys. The fluidity was measured by permanent spiral mold, pre-heated at 450°C. The microstructure was characterized by optical microscope. The fluidity of complex Al-11Si-Cu-Mg eutectic alloy decreased with the increase of La addition. The 1.0 % of La addition led to refinement of silica particles, which reduced the fluidity length by 25%.

Effect of rare-earth metals on the structure and properties of magnesium casting

The influence of rare-earth elements (Sc, Nd, Y) on the structurization, mechanical properties and heat resistance of a widely used magnesium alloy ML5 was studied. The role of intermetallic phases, formed by doping rare-earth metals of magnesium alloy ML5 was shown. The dependence of the morphology and topology of these phases on the chemical composition of magnesium alloys and their influence on the metal structure and properties was determined. It was shown that alloying of magnesium alloys Sc, Nd and Y reduces the intermetallic phase. It was found that spherical intermetallides of smaller-sized groups had a greater impact on improving the mechanical properties of magnesium alloys, and heat resistance of the alloy was determined by the number of a heat-resistant intermetallic phase. It was found that the ultimate strength of alloy ML5 raises with increasing the content of rare-earth elements up to 1.0 %, and the ductility increases only when the content of elements is in the range of 0.05...0.1 %. Applying rare-earth metals, when smelting magnesium alloy ML5 provides an increased level of mechanical properties and heat resistance of castings, which makes it promising in the development of new machines and units.

Обработка угольной золы предприятий энергетики в процессах бактериального выщелачивания редкоземельных металлов

The flotation process of power plants’ ash-slag materials treatment is considered in the article. The original method related to preparing of ash-slag waste before their further bioleaching processing is proposed. The positive results of rare earth metals extraction efficiency increase by bioleaching are obtained. The essence of proposed approach is as follows. Coal combustion’s ash-slag waste is mixed with water to obtain a fine suspension, in which the carbonaceous reagent is injected. Flotation treatment of ash suspension is carried out in mechanical flotation machine with flotation time equal to 15-18 min and air flow rate equal to about 0.7-0.8 m3/(m2·min). The chamber product as treated ash suspension is going to the separation in open hydrocyclone. In such a case the concentration product in the form of ash product is derived to special site, and hydrocyclone overflow is directed to the clearing in pressure flotation machine for extraction of metal ions from the liquid. A positive effect of rare earth metals’ extraction rising related in particular to scandium about 26.6-30.3%, yttrium — 28-34.7%, lanthanum — 50.5-21.5%, as well as precious metals such as gold — 18.7-21.6%, silver — 11.4-21.4% is obtained.

Effects of Rare Earth on the Inclusions and Mechanical Properties of Austenitic Stainless Steel

The effects of rare earth metals on the inclusions and the mechanical properties of 21Cr11Ni austenitic steel were studied by scanning electron microscope (SEM) and energy spectrum analysis. The results show that the morphologies and sizes of inclusions in 21Cr11Ni stainless steel are changed, and rare earth played a very good role of modifying inclusions. The fracture mode of 21Cr11Ni stainless steel is typical cleavage fracture, but quasi-cleavage and dimple fracture after adding RE into the steel. The transverse impact toughness of 21Cr11Ni stainless steel is improved obviously by RE. In comparison with 21Cr11Ni stainless steel without RE, the transverse impact toughness of 21Cr11Ni stainless steel with RE is increased 25.33% at-40°C, and the room temperature strength are improved, the elongation and reduction of area have been improved 9.18%, 12.71% respectively.

Effect of Rare Earth Metals on Microstructure and Impact Property of Duplex Stainless Steel

The effect of rare earth element on structure and mechanical properties of 2205 duplex stainless steel were studied by metallographic examination, scanning electron microscope (SEM), tensile test and impact test. The results show that the proper amount of rare earth can refine microstructure of 2205 duplex stainless steel. Fracture is changed from cleavage to ductile fracture by adding RE to 2205 duplex stainless steel. 2205 duplex stainless steel containing 0.05% RE can improve its impact toughness, and the transverse impact toughness is increased 15.56% at -20°C respectively comparing with that of 2205 duplex stainless steel without RE.

Thermodynamic Analysis and Observation of Inclusions in 2205 Duplex Stainless Steel with Rare Earth Metals

The effect of rare earth metals on modifying inclusions of 2205 duplex stainless steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 2205 duplex stainless steel. According to the composition of 2205 duplex stainless steel liquid and thermodynamic data, it may calculate and predict the kinds of RE inclusions. And the result shows that aluminosilicate complex inclusion and sulfide inclusion can be entirely replaced by RE2O2S and RES that are spherical.

Effect of rare earth metals on solidification behaviour in nickel based superalloy

The effect of rare earth metals (REMs) on the microstructure and segregation during solidification in a highly alloyed Ni based superalloy was investigated. Rare earth metals considerably decrease the amounts of coarse columnar grains and increase the amounts of equiaxed grains. They are segregated to the interdendritic regions mainly as the precipitate of Ni5Ce. Both the dimension and distribution of γ′ particles and MC carbide are modified by REM. Eutectic (γ+γ′), Laves phase, δ phase and σ phase are precipitated in the interdendritic regions because of the serious segregation of niobium and titanium aggravated by REM. The differential thermal analysis indicates that the precipitation temperature of phases and the solidification sequence of the superalloy can be changed due to the additions of REM.

Effects of Ce on the Inclusions and Mechanical Properties of 2Cr13 Stainless Steel

The effects of rare earth metals on the inclusions and the mechanical properties of 2Cr13 stainless steel were studied by metallographic examination, scanning electron microscope (SEM) and energy spectrum analysis. The results show that the morphologies and sizes of inclusions in 2Cr13 stainless steel are changed, and rare earth metals played a very good role of modifying inclusions. The fracture mode of 2Cr13 stainless steel is typical cleavage fracture, but quasi-cleavage and dimple fracture after adding Ce into the steel, and the spherical inclusions of rare earth oxysulfide in the dimple are the main factors for this transformation. The transverse impact toughness of 2Cr13 stainless steel is improved obviously by Ce. In comparison with 2Cr13 stainless steel without Ce, the transverse impact toughness of 2Cr13 stainless steel with Ce is increased 54.55% at -40°C, and the room temperature strength are improved, the elongation and reduction of area have been improved 11.90%, 16.67 respectively.

Effects of Rare Earth Addition on the Inclusions and Mechanical Properties of 2205 Duplex Stainless Steel

The effects of rare earth metals on the inclusions and the mechanical properties of 2205 duplex stainless steel were studied by metallographic examination, scanning electron microscope (SEM) and energy spectrum analysis. The results show that the morphologies and sizes of non-metallic inclusions in 2205 duplex stainless steel are changed, and rare earth metals played a very good role of modifying inclusions. The fracture mode of 2205 duplex stainless steel is typical cleavage fracture, but quasi-cleavage and dimple fracture after adding RE into the steel, and the spherical inclusions of rare earth oxysulfide in the dimple are the main factors for this transformation. The transverse impact toughness of 2205 duplex stainless steel is improved obviously by RE. In comparison with 2205 duplex stainless steel without RE, the transverse impact toughness of 2205 duplex stainless steel with RE is increased 20.49% at -40°C, and the room temperature strength are improved, the elongation and reduction of area have been improved 11.67%, 24.55% respectively.

Effect of Rare Earth Metals on Inclusions and Impact Property of 2205 Duplex Stainless Steel

The effect of rare earth metals on inclusions and impact toughness of 2205 duplex stainless steel were studied by SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 2205 duplex stainless steel. The result shows that aluminosilicate compound inclusion and sulfide inclusion can be entirely replaced by RE2O2S and RES. Fracture is changed from cleavage to ductile fracture by adding RE to the 2205 duplex stainless steel, and the spherical rare earth oxysulfide inclusions-RE2O2S in the dimple are the main factors. The transverse impact value of 2205 duplex stainless stainless steel has been improved obviously by RE. The transverse impact value of RE-2205 is increased 20.49% at the temperature of -40°C, comparing with 0RE-2205.

The effect of rare earth metals on the microstructure and electrochemical corrosion behavior of lead calcium grid alloys in sulfuric acid solution

The effect of the rare earth element lanthanum (La) on the microstructure of lead–calcium grid alloys was studied by the metallographic microscope. A comparison of the electrochemical corrosion behavior of the new and traditional grid alloys was investigated by cyclic voltammetry (CV), A.C. impedance and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to study the surface morphology of anodic films of Pb–Ca–Sn–Al–Re alloys formed in sulfuric acid solution at 1.3 and 0.9 V for 2 h. The morphology of the corrosion layer was analyzed by SEM after the constant current corrosion test. The results show that an appropriate content of La can effectively (1) increase the fineness of the grain of Pb–Ca–Sn–Al alloys, (2) increase the growth of PbO 2 film, and (3) make the anodic film formed at 1.3 V become fine and compact. Alloys with contents of 0.01 wt.%, 0.03 wt.% and 0.1 wt.% La were shown satisfactory results. La also can decrease the growth of Pb(II) film, purify and increase the density of the anodic film at 0.9 V, especially for La content of 0.03 wt.% and 0.1 wt.%. Moreover, La can improve the corrosion resistance of Pb–Ca–Sn–Al alloys, particularly for a La content of 0.01 wt.%.

Effect of rare earth metals on microstructure and corrosion resistance of Zn–0·18Al coatings

Effect of rare earth (RE) metals addition on the microstructure, formation of Fe–Zn intermetallics and corrosion resistance of the batch galvanising Zn–0·18Al coating were studied. Microstructure of the coating was observed using optical microscopy, scanning electron microscopy and transmission electron microscopy. Salt spray test and surface potential measurement were employed for corrosion resistance determination. The results show that the addition of RE can improve bath liquidity, refine surface spangles, stabilise the Fe2Al5 inhibition layer, decrease coating thickness and enhance corrosion resistance of the coating. However, corrosion resistance of the coating did not increase continuously with increasing RE content and the optimum RE content lies between 0·045 and 0·069% in the experiment. Mechanism of RE on the corrosion resistance of the galvanised coating was briefly analysed.

Study on the effect of rare earth metal triflates as initiators in the cationic curing of DGEBA/γ-valerolactone mixtures and characterization of the thermosets obtained

Abstract The thermal cationic curing of mixtures in different proportions of diglycidylether of bisphenol A (DGEBA) with γ-valerolactone (γ-VL) initiated by scandium, ytterbium and lanthanum triflates or a conventional BF3·MEA initiator was investigated. The non-isothermal differential scanning calorimetry (DSC) experiments at a controlled heating rate were used to evaluate the evolution of the reactive systems. BF3·MEA and rare earth metal triflates initiated curing systems follow a different evolution. Among rare earth metal triflates tested, the scandium was the most active initiator. The phenomenological changes that take place during curing were studied and represented in a time-temperature-transformation (TTT) diagram. Some characteristics of the materials were also evaluated.

Effect of rare-earth metals (Y, La, and Ce) on the corrosion and mechanical properties of aluminum-manganese alloy

Effect of some rare-earth metals (yttrium, cerium, and lanthanum) on the corrosion-electrochemical and mechanical properties of an aluminum-manganese alloy of eutectic composition (1.9% Mn) in a neutral medium was studied.

Application of EIS to assess the effect of rare earths small addition on the corrosion behaviour of Zn–5% Al (Galfan) alloy in neutral aerated sodium chloride solution

The effect of rare earth metal (Gd, Dy, Er, and Y) small additions on the corrosion behaviour of Zn–5% Al (Galfan) alloy has been investigated. The corrosion resistance of Zn–5Al–0.1Gd, Zn–5Al–0.1Dy, Zn–5Al–0.1Er, and Zn–5Al–0.1Y alloys has been assessed by 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 the Galfan alloy. EIS results showed that rare earths’ addition significantly improves the corrosion behaviour of Galfan. 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.