Solubility Of Ce Research Articles

Microstructural refinement of an Al-Ce-Mg alloy via Shear Assisted Processing and Extrusion

Al-Ce alloys have attracted recent interest because of their high thermal stability due to the low solubility of Ce in the Al matrix. The Al11Ce3 eutectic phase gives excellent strain hardening behavior and moderate high-temperature strength in the as-cast state. However, its strengthening effect is limited by its coarse as-cast structure. Therefore, alternative manufacturing methods such as additive manufacturing or equal channel angular pressing have been applied to refine the Al11Ce3 phase to good effect. However, these techniques are both expensive and time-consuming. Therefore, this study aims to use Shear Assisted Processing and Extrusion (ShAPE), an emerging solid phase processing technique that is more easily scalable than the previously mentioned methods. ShAPE can produce useful cross-sections of an Al-8Ce-4Mg alloy while refining the Al11Ce3 phase to produce a higher strength material. It was found that a low temperature ShAPE process can improve the room temperature yield strength by ∼60 % compared to a binary Al-4Mg alloy. Additionally, the high-temperature yield strength of the Al-Ce alloys increased by 20 %, with a simultaneous 15 % improvement in ductility compared to the binary Al-Mg alloy. These results highlight the potential for ShAPE as a processing technique for Al-Ce alloys.

The Influence of Rare Earth Ce on the Microstructure and Properties of Cast Pure Copper.

The effects of rare earth Ce on the microstructure and properties of cast pure copper were investigated through thermodynamic calculations, XRD analysis, mechanical testing, metallographic microscopy, and scanning electron microscopy (SEM). The experimental results demonstrate that the reaction between rare earth Ce and oxygen as well as sulfur in copper exhibits a significantly negative Gibbs free energy value, indicating a strong thermodynamic driving force for deoxidation and desulfurization reactions. Ce is capable of removing trace amounts of O and S from copper. Moreover, the maximum solid solubility of Ce in Cu falls within the range of 0.009% to 0.01%. Furthermore, Ce can refine columnar grains while enlarging equiaxed grains in as-cast copper. Upon the addition of rare earth Ce, the tensile strength increased by 8.45%, elongation increased by 12.1%, and microhardness rose from 73.5 HV to 81.2 HV-an increase of 10.5%. Overall, rare earth Ce has been found to enhance both the microstructure and mechanical properties of cast pure copper.

Rare-earth element (REE) remobilization and fractionation in bauxite zones from sedimentary kaolin deposits, western Georgia (USA), Upper Coastal Plain

Rare-earth elements (REE) are critical minerals that are indispensable for high-tech products and technologies. Significant efforts have been focused on the exploration and identification of new and domestic reserves of REE. This study reports geochemical and mineralogical occurrences of accumulated REE with significant fractions of ion-adsorption clays (IAC) within bauxite-kaolin ore, hosted within sedimentary strata. This deposit type can be found throughout portions of Georgia and eastern Alabama (USA) in the Southeast Upper Coastal Plain. These deposits were developed by high degrees of chemical weathering of older, kaolinite-rich sedimentary strata. Several major changes in whole rock mineralogy and geochemistry occurred, leading to the development of zones of REE depletion, fractionation, and accumulation. Depletions of REE in the bauxite zone were significant, with whole rock contents of ∼50% ΣREE relative to average upper continental crust (UCC). Fractionated REE were observed by low La/YbN values (La/YbN = 0.2) due to depletion in LREE (<40% UCC) with concomitant HREE retention (∼1.1–1.3 times UCC). Strongly positive Ce/Ce* anomalies (Ce/Ce* = 1.3), very low ion-exchangeable Ce contents (Ce/LREE = 0.1), and low solubility of Ce (0.9–1.2%) under reducing conditions compared to all other LREE (4.5–9.9%) were further observed. These characteristics were strong indications of REE fractionation that occurred during formation of the bauxite zone. Underlying the bauxite zone, accumulations of the remobilized REE were substantial. At the base of the lower kaolin zone, elevated ion-exchangeable REE contents were notable (11–33% for total REE), and more specifically 11–12% for LREE, ∼28% for ΣTb-Lu, and ∼ 33% for Y. The elevated ion-exchangeable contents coincided with whole rock contents that were ∼ 250% ΣREE relative to UCC. These REE accumulations occurred within organic-rich strata at the base of the section. This setting represents a significant difference relative to the REE accumulations in profiles for the granite-regolith deposit type. These findings highlighted the movement of dissolved REE, accumulation as sorbed species, as well as the potential role that organic ligands play during REE precipitation and sorption processes. These results permit consideration for further research into REE occurrences in clay deposits of sedimentary origin, which have been underexplored compared to granite-regolith REE deposits.

Electrochemical method for determining the solubility of impurities in lead-bismuth eutectic using molten salt electrolytes

Traditional physical methods for measuring solubility were often affected by viscosity, density, and surface tension. In this study, we selected appropriate electrolytes to determine the solubility of impurities in the lead-bismuth circuit at reactor operating temperatures using electrochemical methods. Taking the measurement of the solubility of impurity Ce in liquid Bi as an example, we demonstrated that electrochemical methods can accurately determine its solubility in the LiCl-KCl molten salt. Furthermore, the successful measurement of other impurities such as La, Ce, U, and Mn in lead-bismuth eutectic (LBE) using the designed system has confirmed the universality of this method.

Synthesis and characterization of Eu, Pr-doped garnet with augmented Ce solubility via controlled Fe2O3 reduction

Synthesis and characterization of Eu, Pr-doped garnet with augmented Ce solubility via controlled Fe2O3 reduction

Electrochemical and Spectroscopic Investigation of Solvation and Complexation Effects on Titanium Redox Flow Battery Electrolytes

Titanium (Ti) is a promising elemental redox active species for redox flow batteries (RFBs) as an alternative to the commercially advanced vanadium RFB (V-RFB) due to its 100x availability in the Earth crust1, and 10x lower cost1 (both compared to elemental vanadium). The half-cell potential of the Ti4+/Ti3+ (0.1 V vs SHE) redox couple is closer to the H+/H2 (0V vs SHE) redox couple compared to V3+/V2+ (-0.26V vs SHE)2 thereby mitigating parasitic hydrogen evolution reactions. Thus, the development of Ti-based RFBs (by coupling it with another economical and abundant elemental active) is a promising pathway towards cost effective, grid-scale energy storage and the present work aims to optimize the Ti electrolyte to enable this integration.Ti electrolytes (typically as the anolyte) have been coupled withFe3, 4, Mn5 and Ce6 based catholytes to yield a number of relatively (compared to other aqueous systems) high-potential and high energy density RFBs7. The Ti-Fe, Ti-Mn, and Ti-Ce RFBs have theoretical energy densities of 9 Wh.L-1, 18.9 Wh.L-1, and 19.4 Wh.L-1 respectively7. Electrolyte design with an eye towards improving actives solubility (thereby increasing energy density) and decreasing side-reactions has proven crucial to realizing these systems. For example, deleterious Cl2 evolution reduced the coulombic efficiency of the earliest Ti-Fe RFBs3 and has been overcome by the use of H2SO4 as an alternate supporting electrolyte4. In Ti-Mn RFBs, Mn3+ is highly unstable and inclined to form MnO2. A highly acidic environment or increasing the amount of Mn2+ reduces the disproportionation of Mn3+. Alternatively, the addition of an equal concentration of TiOSO4 with MnSO4 at the catholyte and reducing the maximum operational state of charge to 50%5 reduces MnO2 precipitation. In Ti-Ce RFBs, Ce is the limiting element in terms of solubility as the solubility of Ce is lower (0.5M in H2SO4 and 0.9M in CH3SO3H)6, 8, 9 whereas Ti is highly soluble (up to 5M TiOSO4 in 4M H2SO4). On the other hand, kinetically, Ti is the limiting element with 3x lower rate constant than the Ce redox couple6.Seeking to harness the higher solubility (and hence energy density) of the Ti electrolyte while overcoming the kinetic limitations, we investigated the solubility and the electrochemical reversibility of Ti4+/Ti3+. We characterized the behavior of Ti ions in various supporting electrolytes namely, H2SO4, HCl, HNO3, CH3SO3H by varying the ratio of Ti redox active species to counterion. The diffusion coefficients of the Ti3+ and Ti4+ ions were measured and the impact of the Tix+ to solvating ligand ratio was examined (see example in Fig.1(a)). Spectroscopically determining the coordination structures around solvated Tix+ ions10, we identified electrolyte compositions that result in increasing ionic conductivity (Fig.1(b)). The effect (or lack thereof) of solvation structure on the Ti3+/Ti4+ redox rate constants were examined and correlated to the calculated solvation energy (hence distinguishing between inner- and outer-sphere processes) and the role of catalysts was addressed. Finally, utilizing the electrochemical Thiele modulus framework11, 12, the best (highest energy density coupled with optimal transport and kinetic properties) Ti electrolyte compositions for Ti-Fe, Ti-Mn and Ti-Ce RFBs has been identified.

Structural and electronic properties of Ce‐doped Ti4O7 based on experiments and first‐principles calculations

AbstractA series of Ti4O7 powders with different Ce‐cation doping concentrations were successfully prepared through a new strategy combining the wet chemical method and hydrogen thermal reduction. It is shown that Ce, entering the lattice of Ti4O7 during the reduction process, only occurs in the form of Ce3+, and the solubility of Ce is equal to 8.93 at.%. Furthermore, the electrical conductivity of Ce‐doped Ti4O7 powders was tested for the first time and theoretically explained by the first‐principles calculations. It was revealed that Ce provides a negative effect on the electrical conductivity of Ti4O7 powders, which is due to the decrease in the number of electronic states near the Fermi energy level caused by the introduction of Ce.

Thermal phase transformation behavior of florencite and implications on the leaching recovery of rare earth elements (REEs)

Florencite-(Ce) was synthesized to investigate its thermal phase transformation behavior. The XRD results showed that florencite-(Ce) started to dehydroxylate in the temperature range of 400–500 °C, and the crystal structure was decomposed at 600–700 °C, while further elevating the calcination temperature to over 900 °C resulted in the recrystallization of CePO4. TGA-DTA showed that the complete decomposition and the recrystallization occurred at around 677 °C and 971 °C, respectively. Acid leaching tests were performed on the materials to investigate the effect of calcination on the Ce recovery. It was found that the gradual decomposition of florencite resulted in the increase in the solubility of Ce. To reveal the potential effects of kaolinite and coal coarse refuse on the thermal phase transformation, the mixtures were calcined at 700 °C and 1000 °C, respectively. XRD, DTA, and acid leaching test results showed that the phase transformation of florencite-(Ce) was an independent reaction.

Solubility and Valence Variation of Ce in Low-Alkali Borosilicate Glass and Glass Network Structure Analysis.

Low-alkali borosilicate glass was used as the immobilization substrate, and Ce was used to replicate the trivalent and tetravalent actinides, in order to create simulated waste glass through melt heat treatment. The valence of Ce and solubility of CeO2 in waste glass were studied as well as its network structure and thermal and chemical stability. The solubility of Ce in waste glass was examined by XRD and SEM. The network structure was examined by Raman spectroscopy. The valence of Ce was determined by X-ray photoelectron spectroscopy. Thermal analysis and product consistency (PCT) were employed to determine the thermal and chemical stability of waste glasses. The results show that the solubility of cerium in low-alkali borosilicate glasses is at least 25.wt.% and precipitates a spherical CeO2 crystalline phase when it exceeds the solid solution limit; Ce is immobilized in the glass by entering the interstices of the glass network. Depolymerization and the transition from [BO3] to [BO4] occurs when CeO2 doping levels rise. About 60 percent of Ce4+ is converted to Ce3+, and the thermal stability of glass rises then falls with the increase of CeO2. All samples exhibit strong leaching resistance, with the average mass loss of Ce at 28 days being less than 10-4 gm-2d-1.

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Use of Mixed Methanesulfonic Acid/Sulfuric Acid as Positive Supporting Electrolyte in Zn-Ce Redox Flow Battery

The effect of different positive supporting electrolytes on the performance of a bench-scale Zn-Ce redox flow battery (RFB) has been studied. The effectiveness of mixed methanesulfonic/sulfuric acid, mixed methanesulfonic/nitric acid and pure methanesulfonic acid has been assessed and compared on the basis of the cyclic voltammetric response for the Ce(III)/Ce(IV) redox couple and galvanic charge-discharge of a bench-scale Zn-Ce RFB. The Ce(III)/Ce(IV) reaction exhibits faster kinetics and the RFB exhibits higher coulombic efficiency and long-term performance over ∼40 charge-discharge cycles in the mixed 2 mol l−1 MSA-0.5 mol l−1 H2SO4 electrolyte compared to that achieved in the commonly used 4 mol l−1 MSA electrolyte due to lower H+ crossover and higher Ce(IV) solubility. The coulombic efficiency fade rate in the mixed MSA-H2SO4 electrolyte is 0.55% per cycle over 40 charge-discharge cycles, while the fade rate is 1.26% in the case of 4 mol l−1 MSA. Furthermore, the positive electrode reaction is no longer the limiting half-cell reaction even at the end of long-term battery charge-discharge operation. This work shows that a mixed MSA-H2SO4 acid electrolyte may be a better option for the positive side of a Zn-Ce RFB as a large-scale energy storage device.

Double-Site Substitution of Ce into (Ba, Sr)MnO3 Perovskites for Solar Thermochemical Hydrogen Production

Solar thermochemical hydrogen production (STCH) is a renewable alternative to hydrogen produced using fossil fuels. While serial bulk experimental methods can accurately measure STCH performance, screening chemically complex materials systems for new promising candidates is more challenging. Here we identify double-site Ce-substituted (Ba,Sr)MnO3 oxide perovskites as promising STCH candidates using a combination of bulk synthesis and high-throughput thin film experiments. The Ce substitution on the B-site in 10H-BaMnO3 and on the A-site in 4P-SrMnO3 lead to 2-3x higher hydrogen production compared to CeO2, but these bulk single-site substituted perovskites suffer from incomplete reoxidation. Double-site Ce substitution on both A- and B-site in (Ba,Sr)MnO3 thin films increases Ce solubility and extends the stability of 10H and 4P structures, which is promising for their thermochemical reversibility. This study demonstrates a high-throughput experimental method for screening complex oxide materials for STCH applications.

The solubility, microstructure, and chemical durability of Ce‐doped YIG ceramics designed as actinide waste forms

Yttrium iron garnet (YIG) is a potential matrix for immobilizing high-level radioactive waste (HLW) due to its high actinide solubility and chemical flexibility. In this study, Ce was employed as a surrogate of Pu. A series of Y3-xCexFe5O12 (0 ≤ x ≤ 1) samples were prepared by solid-state sintering at 1400°C to investigate the solubility, microstructure, and chemical durability of Ce-doped YIG. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the solubility of the Ce in a single garnet was 32 mol% at synthesis temperature of 1400°C. The SEM analysis indicated the YIG ceramic grain growth and compactness as Ce concentrations increased. The XPS analysis indicated that the amount of Ce4+ out of the total Ce increased as the CeO2 doping increased, and the maximum value was more than 75.9% in the sample synthesis at 1400°C. Static leaching experiments were also conducted on the single Ce-doped garnet synthesized at 1400°C. The normalized LRCe and LRY release rates were approximately 10−4 and 10−5 g m−2 d−1 after 42 days, respectively. The chemical durability was comparable to other ceramic matrices (such as pyrochlore and zircon, among others). These results demonstrated that YIG ceramics are suitable for immobilizing HLW, such as Pu or U. Highlights The solubility of Ce in single-phase YIG was 32 mol% at 1400°C. Grain size and compactness increased Ce content. The concentration of Ce4+ in total Ce of sample could be over 75.9%. The obtained YIG ceramics exhibit excellent chemical stability. Novelty Statement Y3-xCexFe5O12 ceramics were prepared by solid-state sintering and the solubility, microstructure, and chemical durability were investigated. The solubility of Ce was 32 mol% at 1400°C. The obtained YIG ceramics exhibit excellent chemical stability.

Enhanced thermal coarsening resistance in a nanostructured aluminum-cerium alloy produced by additive manufacturing

Decreasing microstructural length scales to the nanoscale is a proven way of increasing strength, but the intrinsic metastability of such structures typically makes them susceptible to thermally activated coarsening. Recent advances in additive manufacturing permit bulk-nanostructured materials to be produced through rapid solidification, but like other metastable materials the as-built structures typically coarsen rapidly with even modest thermal exposure. Here, selective laser melting is employed to produce an Al-Ce-based alloy with high mechanical strength arising from the as-built microstructure, which can be controlled by build conditions. In addition, the alloy exhibits extreme resistance to thermal coarsening up to 400 °C and superior strength retention compared to conventional Al alloys after extended thermal exposure. The near-zero solubility of Ce in Al and potent solid solution strengthening of Mg enable this behavior without requiring heat treatment. This result demonstrates that combining insoluble alloying elements with additive manufacturing is a viable method of producing exceptionally stable bulk nanoscale alloys.

Phase Equilibria of the Mg-Gd-Ce System at 500 °C

The phase equilibria of the Mg-Gd-Ce system at 500 °C were investigated by means of the electron probe microanalysis (EPMA) and x-ray diffraction (XRD) on equilibrated alloys. The existence of the so-called normal tetragonal CeMg12(I) and long-range ordered CeMg12(II) was confirmed in the present work. The following five three-phase equilibria were well determined: (1) (Mg) + CeMg12(I) + Ce5Mg41, (2) (Mg) + Ce5Mg41 + GdMg5, (3) Ce5Mg41 + GdMg5 + (Ce,Gd)Mg3, (4) (Ce,Gd)Mg3 + GdMg2 + (Ce,Gd)Mg and (5) (Ce,Gd)Mg + (δCe) + (βCe). The solubility of Ce in GdMg5 and in GdMg2 was measured to be 7.8 and 8.7 at.% Ce, respectively. The solubility of Gd in CeMg12(I), in Ce5Mg41 and in (δCe) were measured to be 1.0, 4.6 and 2.4 at.% Gd, respectively. Two continuous series of solid solutions form between GdMg3 and CeMg3, and between GdMg and CeMg. The overall isothermal section at 500 °C was constructed based on the present data with a few extrapolations.

Studies of ferroelectric and magnetic phase transitions in Pb(Fe0.5Nb0.5)1-xCexO3 multiferroic ceramics

Multiferroic Pb(Fe0.5Nb0.5)1-xCexO3 (x = 0.025, 0.05, 0.075, 0.10) ceramic compositions were prepared by solid state synthesis and usual sintering. XRD studies have shown a formation of the perovskite structure in all the compositions studied. However a small amount of pyrochlore phase was detected in Ce-doped compositions with x ≥ 0.075. Scanning electron microscopy studies and elemental analysis have shown that at the boundaries of the large grains of nearly pure PbFe0.5Nb0.5O3 there exist a lot of small submicron grains enriched by Ce. Concentration dependencies of the unit-cell parameter and temperatures of ferroelectric and magnetic phase transitions also imply that solubility of Ce in PFN does not exceed ≈ 2 at.%.

Structures and Free Energies of Cerium Ions in Acidic Electrolytes.

The Ce3+/Ce4+ redox potential changes with the electrolyte, which could be due to unequal anion complexation free energies between Ce3+ and Ce4+ or a change in the solvent electrostatic screening. Ce complexation with anions and solvent screening also affect the solubility of Ce and charge transfer kinetics for electrochemical reactions involving waste remediation and energy storage. We report the structures and free energies of cerium complexes in seven acidic electrolytes based on Extended X-ray Absorption Fine Structure, UV-vis, and Density Functional Theory calculations. Ce3+ coordinates with nine water molecules as [Ce(H2O)9]3+ in all studied electrolytes. However, Ce4+ complexes with anions in all electrolytes except HClO4. Thus, our results suggest that Ce4+-anion complexation leads to the large shifts in standard redox potential. Long range screening effects are smaller than the anion complexation energies but could be responsible for changes in the Ce solubility with acid.

Phase relationships in the Ce–Nd–B system at 773 K

Abstract Phase relationships in the Ce-Nd-B ternary system at 773 K were investigated by means of X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy techniques. Six borides, i. e. CeB4, CeB6, NdB4, NdB6, NdB66 and Nd2B5 are confirmed in this work. No ternary compound was observed. CeB4 and NdB4 were discovered to form the continuous solid solution phase (Ce,Nd)B4, CeB6 and NdB6 also form the solid solution phase (Ce,Nd)B6. The maximum solid solubility of Ce in (Ce,Nd)2B5 phase is 46.5 at.%. The isothermal section of the Ce-Nd-B ternary system at 773 K consists of 3 three-phase regions, 7 two-phase regions and 7 single- phase regions.

Phase relationships in the Ce–Nd–B system at 773 K

Abstract Phase relationships in the Ce-Nd-B ternary system at 773 K were investigated by means of X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy techniques. Six borides, i. e. CeB4, CeB6, NdB4, NdB6, NdB66 and Nd2B5 are confirmed in this work. No ternary compound was observed. CeB4 and NdB4 were discovered to form the continuous solid solution phase (Ce,Nd)B4, CeB6 and NdB6 also form the solid solution phase (Ce,Nd)B6. The maximum solid solubility of Ce in (Ce,Nd)2B5 phase is 46.5 at.%. The isothermal section of the Ce-Nd-B ternary system at 773 K consists of 3 three-phase regions, 7 two-phase regions and 7 single- phase regions.

Effect of thermal cycle and Bi / Eu doping on the solubility of Ce in YIG

In this work, garnet materials with the composition of Y3-x-y-zCexBiyEuzFe5O12 (x = 0.25, 0.50 and y = 0.00, 0.10 and z = 0.00, 0.25) were synthesized from Fe2O3, Y2O3, CeO2, Bi2O3 and Eu2O3 via the solid state method. Three different thermal cycles were investigated to dissolve Ce in YIG and the optimal cycle was determined as 6 h at 1420°C. By using the optimized cycle, the effect of Bi and Eu additives on the solubility of Ce in YIG was studied. The results revealed that Eu can increase the solubility of Ce with a suitable thermal cycle. The Bi doping can cause problems in Ce solubility due to its larger ionic radius than that of Y and Ce. The secondary and impurity phases are a result of Ce solubility limitation.