RE Inclusions Research Articles

Solidification-induced nonuniformity in U–Zr–RE metallic nuclear fuel rods

Metallic fuel is being developed for the next generation of sodium-cooled fast reactors due to its safety and fuel cycle economics through spent fuel reprocessing technology. After spent fuel reprocessing, rare earth elements that are immiscible with Uranium and Zirconium are included in the raw material for metallic fuel. Achieving a uniform composition and microstructure of RE inclusions is challenging because phase separation and temperature inhomogeneities during solidification lead to non-uniform composition and microstructure. This study explores the solidification and inclusion formation of U–Zr–RE metallic fuel rods. We show how RE inclusions are formed in the U–Zr matrix and how temperature inhomogeneities during solidification control the inclusion size distribution and edge migration of RE inclusions along the U–Zr–RE rods. Understanding the inhomogeneity of inclusions due to solidification can provide hints for making homogeneous nuclear fuel rods.

One-step synthesis of 1,4-butanediol from maleic anhydride by gas-phase selective hydrogenation over xRe/CuZnZr catalysts

Producing 1,4-butanediol with selective hydrogenation of maleic anhydride has significant financial benefits. This work reported a “green” one-step method for preparing 1,4-butanediol from maleic anhydride in a gas-phase fixed bed continuous flow reactor over an efficient 2Re/CuZnZr catalyst for the first time. In this paper, CuZnZr composite metal oxides were synthesized using the co-precipitation technique, followed by impregnation of Re to produce xRe/CuZnZr catalysts. The study aimed to investigate the effects of including Re on the catalyst's structure and performance. The results obtained from the characterization indicate that the presence of Re in the system restricts the growth of Cu0 grains. In addition, the inclusion of Re facilitated the utilization of ZnO as an effective spacer, reducing the size and quantity of Cu species agglomerates and enhancing active metal dispersion. This phenomenon may be attributed to being the primary factor responsible for the observed enhancement in the activity of the maleic anhydride hydrogenation reaction. Meanwhile, Re facilitated the transformation of γ-butyrolactone, an intermediate resulting from the hydrogenation of maleic anhydride into 1,4-butanediol. The 2Re/CuZnZr catalyst exhibited favorable catalytic activity under the conditions of 190 °C and 6 MPa, resulting in the complete conversion of maleic anhydride and a selectivity of 85 % towards 1,4-butanediol. The catalyst showed consistent catalytic performance throughout the 200 h. The finding about the impact of Re promoter on Cu-based catalysts has the potential to yield a highly efficient catalytic system for alcohol generation.

Segregation of rare earth elements in the melting process for injection casting of U–Zr metallic fuels

We investigated the segregation behavior of rare earth elements (RE = La, Ce, Pr, and Nd) in the injection casting process of U–Zr metallic fuel using the characterization methods such as density measurement, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma−atomic emission spectroscopy. Injection casting of the metallic fuels with nominal compositions of U–10Zr−xRE (in wt%, x = 5, 7, and 10) resulted in the fuel slugs exhibiting similar compositions regardless of the RE content charged in the melting crucible. The microstructure observations revealed that RE-segregated layer occupied the upper region of the melt-residue in case of injection casting of U–10Zr−7RE and U–10Zr−10RE while the melt-residue of U–10Zr−5RE was relatively homogenous in terms of RE distribution. The segregation was caused by the immiscibility of RE in U–Zr alloys. When the RE content was higher than 5 wt%, the thickness of the segregation layer increased with the amount of the charged RE. RE inclusions migrated toward the upper region of the molten alloy owing to the different densities and specific gravities as compared to that of the U–Zr alloy, which led to the non-uniformity in the composition of the melt-residue after injection casting of U–10Zr−7RE and U–10Zr−10RE. The migration behavior of RE during melting was suggested to be induced by the fractional crystallization owing to the immiscibility and the difference in solidification temperature.

Rhenium and Molybdenum as Diffusion Inhibitors in Catalytic Metal Particles for growth of Ultra-Long Carbon Nanotubes (CNTs)

ABSTRACTBulk production by Chemical Vapor Deposition (CVD) of ultra-long Carbon Nanotubes (CNTs) with lengths greater than several centimeters is desirable for materials applications, but is not presently feasible. A principal reason for this limitation is cessation of CNT growth due to erosion of the nano-sized catalyst particles from which the CNTs nucleate and grow: at elevated CVD growth temperatures, atoms of catalytic metal detach and diffuse away from the particles, resulting in erosion and eventual deactivation of the particles. Recently, a novel idea was introduced to slow this diffusion and erosion by including heavy refractory metals with the catalyst metals in the nanoparticles. Here are presented recent and ongoing investigations into this method. The metal system investigated uses iron as catalyst and rhenium as diffusion inhibitor. Results show that inclusion of Re in the catalyst particles will substantially increase the catalysts particle lifetimes, and hence the growth time of the CNTs produced. These results are compared to previous results obtained using the iron/molybdenum system of catalyst/inhibitor.

Study of Rare Earth Additions Effect on the Solidification and Properties of 4130 Steel

This paper covers a set of experiments where two different rare earth additions were made to 4130 steel. A thermal analysis system was employed to measure solidification reactions and determine whether changes from the baseline occurred. Keel block castings were also poured and then machined into tensile bars. Mechanical testing found an increase in strength. Electron microscopy found RE oxysulfides had formed in the steel. Examination of the cooling rate curves noted the formation of additional phases during the solidification of the RE treated steels. The peritectic and solidus temperatures of the treated steels increased, indicating that the RE inclusions acted as heterogeneous nuclei for austenite during freezing.

Thermal Analysis of Rare Earth Grain Refined 4130

This paper discusses the thermal analysis of rare earth grain refined 4130. To accomplish this, heats of 4130 Baseline, 0.3 wt% RE silicide, and 0.3 wt% EGR were poured in a thermal analysis cup with a single S-type thermocouple at the bottom. A data acquisition system recorded the cooling curves whose values were compared to reference data. The samples were sectioned and macroetched. A scanning electron microscope analyzed the samples to determine inclusion composition. It was observed that the liquidus was similar for all the samples; however, the peritectic temperature for the 0.3 wt% RE and 0.3 wt% EGR was higher than the Baseline. This increase was thought to be due to RE oxysulfides acting as heterogeneous nuclei for austenite. A number of additional peaks appeared in the grain refined steels that seem to be related to the formation of RE oxysulfides during solidification. Macroetching found a larger equiaxed region in the TA cups from the treated steels and a finer structure. The improvement in microstructure seems related to the RE inclusions and peritectic temperature increase.

Effects of Rare Earth on the Microstructure and Impact Toughness of H13 Steel

Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM) can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM additions. In this present work, the microstructure evolution and mechanical properties of H13 steel with rare earth additions (0, 0.015, 0.025 and 0.1 wt.%) were investigated. The grain size, inclusions and fracture morphology were systematically studied by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that REM addition of 0.015 wt.% can result in good improvement of performance compared to the REM additions of 0.025 wt.% and 0.1 wt.%. It is found that the impact toughness is significantly enhanced with the addition of 0.015% REM, which can be improved 90% from 10 J to 19 J. Such an addition of REM can result in a huge volume fraction of finer and more dispersive inclusions which are extremely good to toughness.

High- and low-Am RE inclusion phases in a U–Np–Pu–Am–Zr alloy

Structural, microstructural, and microchemical data were collected from rare-earth inclusions in an as-cast U–Pu–Zr alloy with ∼3at.% Am, 2% Np, and 9% rare-earth elements (La, Ce, Pr, and Nd). Two RE phases with different concentrations of Am were identified.The composition of high-Am RE inclusions is ∼2–5at.% La, 15–20% Ce, 5–10% Pr, 25–45% Nd, 1% Np, 5–10% Pu, and 10–20% Am. Some areas also have O, although this does not appear to be an essential part of the high-Am RE phase. The inclusions have a face-centered cubic structure with a lattice parameter a∼0.54nm.The composition of the only low-Am RE inclusion studied in detail is ∼35–40at.% O, 40–45% Nd, 1–2% Zr, 4–5% La, 9–10% Ce, and 6–7% Pr. This inclusion is an oxide with a crystal structure similar to the room-temperature structure of Nd2O3. Microstructural features suggest that oxidation occurred during casting, and that early crystallization of high-temperature oxides led to formation of two distinct RE phases.

Effect of Rare Earth on the Inclusions and Pitting Resistance of Austenitic Stainless Steel

The anodic polarization curves of 21Cr-11Ni austenitic stainless steels with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods. The effect of RE on pitting corrosion resistance of 21Cr-11Ni stainless steels has been studied by the metallographic examination. The results show that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES after adding RE to 21Cr-11Ni stainless steesl. RE makes sulfide, and other irregular inclusions change to dispersed round or oval-shaped RE inclusions, effectively inhibits the occurrence of pitting corrosion, thereby enhancing the corrosion resistance of 21Cr-11Ni austenitic stainless steels.

Thermodynamic Analysis and Observation of Inclusions in RE-Austenitic Stainless Steel

The effect of RE on modifying inclusions of 21Cr-11Ni austenitic stainless steel was studied by SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 21Cr-11Ni stainless steel. The result shows that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES.

Thermodynamic Analysis and Observation of Inclusions in 10PCuRE Weathering Steel

The effect of RE on modifying inclusions of 10PCu weathering steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 10PCu weathering steel. The result shows that aluminosilicate inclusions are modified to round RE complex inclusions after adding RE to 10PCuRE steel.

Thermodynamic Analysis and Observation of Inclusions in H13 Die Steel with Rare Earth

The effect of RE on modifying inclusions of H13 die steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in H13 die steel. The result shows that sulfide inclusions are modified to round RE complex inclusions after adding RE to H13 die steel.

Thermodynamic Analysis and Observation of Inclusions in Ferritic Stainless Steel with Rare Earth

The effect of RE on modifying inclusions of 430 ferrite stainless steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 430 ferrite stainless steel. The result shows that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES.

Effect of Rare Earth on the Inclusions and Pitting Resistance of Duplex Stainless Steel

The anodic polarization curves of 2205 duplex stainless steel with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods, The effect of rare earth on pitting corrosion resistance of 2205 duplex stainless steel has been studied by the metallographic examination. The results show that RE can effectively depress pitting corrosion, while the irregular inclusions of Al2O3, sulfide in the shape of clump are transformed into tiny dispersive round or oval RE inclusions, and it plays a good role in pitting resistance.

Effect of Rare Earth on the Inclusions and Pitting Resistance of Ferrite Stainless Steel

The anodic polarization curves of 430 ferrite stainless steels with various RE contents in 3.5% NaCl neutral solutions have been measured by electrochemical methods. The effect of RE on pitting corrosion resistance of 430 ferrite stainless steels has been studied by the metallographic examination. The results show that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES after adding RE to 430 ferrite stainless steesl. RE makes sulfide, and other irregular inclusions change to dispersed round or oval-shaped RE inclusions, effectively inhibits the occurrence of pitting corrosion, thereby enhancing the corrosion resistance of 430 ferrite stainless steels.

Thermodynamic Analysis and Observation of Inclusions in RE-2Cr13 Stainless Steel

The effect of Ce on modifying inclusions of 2Cr13 stainless steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 2Cr13 stainless steel. The result shows that MnS can be entirely replaced by Ce2O2S and CeS that are spherical.

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 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.

Effect of Ce on Inclusions and Impact Property of 2Cr13 Stainless Steel

Abstract The effect of Ce on inclusions and impact toughness of 2Cr13 stainless steel were studied by SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 2Cr13 stainless steel. The result shows that Al 2O 3 and MnS can be entirely replaced by Ce 2O 2S and CeS. Fracture is changed from cleavage to ductile fracture by adding Ce to the 2Cr13 stainless steel, and the spherical rare earth oxysulfide inclusions (Ce 2O 2S) in the dimple are the main factors. The transverse impact value of 2Cr13 stainless steel has been improved obviously by Ce. The transverse impact value of RE-2Cr13 is increased by 54.55% at the temperature of — 40 °C, comparing with 0RE-2Cr13.

The precipitation diagram of [Ce]‐[O]‐[S] in liquid iron and its application

A space precipitation diagram of [Ce]‐[O]‐[S] in pure liquid iron has been constructed utilising recent experimental thermodynamic data gathered on allied equilibrium systems of RE‐O, RE‐S and RE‐O‐S. A quantitative correlation between the activities of oxygen, sulphur and the constitution of the formed RE inclusions has been found. This correlation was theoretically evaluated through thermodynamic calculation and verified by experimental data concerned with the activities of oxygen and sulphur in liquid iron and the composition of the formed RE inclusions.