Thermal equation of state study of polymorphic phases of Y2O3
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99 GENERAL AND MISCELLANEOUS↗
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Materials Data on Y2O3 by Materials Project
Y2O3 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.22–2.59 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Y3+ atoms to form OY4 tetrahedra that share corners with six equivalent OY6 octahedra, corners with six equivalent OY4 tetrahedra, edges with three equivalent OY6 octahedra, and edges with three equivalent OY4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–55°. In the second O2- site, O2- is bonded to six equivalent Y3+ atoms to form OY6 octahedra that share corners with twelve equivalent OY4 tetrahedra, edges with six equivalent OY6 octahedra, and edges with six equivalent OY4 tetrahedra.
36 MATERIALS SCIENCE↗
Materials Data on Y2O3 by Materials Project
Y2O3 is Corundum-like structured and crystallizes in the cubic Ia-3 space group. The structure is three-dimensional. there are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge and corner-sharing YO6 octahedra. The corner-sharing octahedra tilt angles range from 54–56°. There are a spread of Y–O bond distances ranging from 2.27–2.36 Å. In the second Y3+ site, Y3+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing YO6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Y–O bond lengths are 2.31 Å. O2- is bonded to four Y3+ atoms to form a mixture of distorted edge and corner-sharing OY4 trigonal pyramids.
36 MATERIALS SCIENCE↗
Materials Data on Y2O3 by Materials Project
Y2O3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.25–2.59 Å. In the second Y3+ site, Y3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing YO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Y–O bond distances ranging from 2.21–2.48 Å. In the third Y3+ site, Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.26–2.75 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to five Y3+ atoms to form distorted OY5 square pyramids that share corners with seven OY4 tetrahedra, corners with two equivalent OY4 trigonal pyramids, edges with two equivalent OY6 octahedra, edges with two equivalent OY5 square pyramids, edges with three OY4 tetrahedra, and edges with three equivalent OY4 trigonal pyramids. In the second O2- site, O2- is bonded to four Y3+ atoms to form OY4 tetrahedra that share a cornercorner with one OY6 octahedra, corners with five equivalent OY5 square pyramids, corners with four OY4 tetrahedra, corners with three equivalent OY4 trigonal pyramids, edges with two equivalent OY6 octahedra, an edgeedge with one OY5 square pyramid, and edges with two equivalent OY4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the third O2- site, O2- is bonded to four Y3+ atoms to form distorted OY4 trigonal pyramids that share a cornercorner with one OY6 octahedra, corners with two equivalent OY5 square pyramids, corners with nine OY4 tetrahedra, corners with two equivalent OY4 trigonal pyramids, edges with three equivalent OY5 square pyramids, and edges with two equivalent OY4 trigonal pyramids. The corner-sharing octahedral tilt angles are 37°. In the fourth O2- site, O2- is bonded to four Y3+ atoms to form distorted OY4 tetrahedra that share corners with two equivalent OY6 octahedra, corners with two equivalent OY5 square pyramids, corners with four OY4 tetrahedra, corners with six equivalent OY4 trigonal pyramids, an edgeedge with one OY6 octahedra, edges with two equivalent OY5 square pyramids, and an edgeedge with one OY4 tetrahedra. The corner-sharing octahedral tilt angles are 13°. In the fifth O2- site, O2- is bonded to six Y3+ atoms to form OY6 octahedra that share corners with six OY4 tetrahedra, corners with two equivalent OY4 trigonal pyramids, edges with two equivalent OY6 octahedra, edges with four equivalent OY5 square pyramids, and edges with six OY4 tetrahedra.
36 MATERIALS SCIENCE↗
Materials Data on Y2O3 by Materials Project
Y2O3 crystallizes in the cubic Pn-3m space group. The structure is three-dimensional. Y3+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Y–O bond lengths are 2.29 Å. O2- is bonded to four equivalent Y3+ atoms to form a mixture of corner and edge-sharing OY4 tetrahedra.
36 MATERIALS SCIENCE↗
Materials Data on Y2O3 by Materials Project
Y2O3 is Corundum structured and crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Y3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge, face, and corner-sharing YO6 octahedra. The corner-sharing octahedra tilt angles range from 49–65°. There are three shorter (2.26 Å) and three longer (2.37 Å) Y–O bond lengths. O2- is bonded to four equivalent Y3+ atoms to form a mixture of distorted edge and corner-sharing OY4 trigonal pyramids.
36 MATERIALS SCIENCE↗
Synthesis of Yttrium Oxide Particles for Interfacial Water Radiolysis Studies
Radiolysis of water produces hydrogen gas (H2), posing safety issues for nuclear reactors. Metal oxides can impact H2 formation when water is present on metal oxide surfaces. This presentation focuses on the development of a controllable synthesis of spherical yttrium oxide (Y2O3), that later will be tested for H2 production in water radiolysis. Y2O3 was synthesized via hydrothermal hydrolysis precipitation to form yttrium hydroxide (Y(OH)3), followed by high temperature decomposition to form Y2O3. Various synthesis conditions were tested to determine their impact on particle morphology including reaction time, cooling rate, reactant concentration, and inert atmospheres. Through short reaction times and rapid cooling rate, spherical, relatively uniform particles of 350 nm were obtained. Despite inert atmospheres, carbonate formation occurred in all particles. A calcination temperature of 800°C is necessary to remove impurities. Future work will aim to reduce carbonate formation and improve particle uniformity. The synthetic procedure will be translated to other metal ions to study their impact on interfacial radiolysis.
08 - HYDROGEN↗
Assessing Manufacturability of the Oxide Dispersion Strengthened (ODS) 14YWT Alloy Fuel Cladding Tube Using SolidStir™ Technology
The 14YWT (Fe–14Cr–3W–0.4Ti–0.3Y2O3 (wt.%)) alloy is a potential candidatematerial for fabricating fuel cladding tubes and other structural components to be used in next-generation advanced nuclear reactors. Due to inherent limitations of current processing routes, this research explored a new variant of friction stir processing, commercially referred to as SolidStir™ Extrusion (patent pending) technology from Enabled Engineering to consolidate and extrude 14YWT powder into a fuel cladding tube. Several single-layer and multiple-layer consolidation experiments were carried out in an Inconel 625 die to determine the suitable processing parameters for SolidStir™ extrusion of the 14YWT alloy cladding tube. With these processing parameters, a 16–18 mm long tube of the 14YWT alloy with no visible defects was successfully extruded using this novel technology. Microstructural characterization results obtained using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and transmission electron microscopy will be presented.
Advanced Materials and Manufacturing Technology↗
Development of High Temperature (>700°C) molten Salt Pump Technology for Gen3 Solar Power Tower Systems
Generation 3 Concentrating Solar Power (CSP) Systems require thermal energy storage that can efficiently receive solar heat and deliver it to a working fluid at temperatures greater than 700°C. For liquid systems, the thermal transfer fluid must be phase stable over large temperature ranges. High temperature molten salts meet this criteria, but are difficult liquids to handle. The high heat and salt content can be very corrosive to several different materials that are wetted by the liquid salt. For power tower collectors, the molten salt must be pumped under high pressure to the top of the collector tower. These pumps have impellers and shafts as part of their rotating elements, and under load, require bearings to control shaft movement while rotating. These high temperature pumps require submerged bearings, and thus bearing materials that can withstand the temperature and molten salt contact over long periods of time. This is essential for keeping pump maintenance costs low, and downtime to a minimum. Long running bearing materials is an enabling technology for integrated liquid systems in Generation 3 CSP Systems. Keeping costs low and systems reliable are critical for the broad adoption of Gen 3 CSP Systems. Hayward Tyler, Inc (HTI) proposed development of journal bearing materials for use in vertical pumps designed for pumping high temperature molten salt on both the hot and cold sides of the solar power tower. To complete this objective, HTI utilized the testing capabilities of Oak Ridge National Laboratory (ORNL) and High Temperature System Design (HTSD). Materials would first be selected for static corrosion testing, then downselected for tribological testing. Successful tribologically tested materials would then be downselected for use in additional test regimes. Ten samples were selected for static corrosion testing. Three passed the static testing regime. Two of these materials were downselected for ball material in tribological testing against three metallic alloys: Sintered Y2O3 Partially Stabilized Zirconia YTZP and Silicon Nitride, Grade 147-31N. HTI also proposed collecting data from a thorough bearing test regime using a test rig designed and built as part of this project, and also a conceptual design for a high temperature molten salt vertical pump. HTI withdrew from the project prior to completion of this work and this report reflects only the work completed prior to withdrawal. The completed work produced two papers, one manuscript submitted for publication, and one paper published in the journal Solar Energy Materials and Solar Cells. The papers are: “Tribological behavior of ceramic-alloy bearing contacts in molten salt lubrication for concentrating solar power” and “Material Selection and Corrosion Studies Of Candidate Bearing Materials For Use In Molten Chloride Salt."
14 SOLAR ENERGY↗
Probing the Critical Element Chemistry of Coal-Combustion Fly Ash: Examination of Zircon and Associated Minerals from a Beneficiated Kentucky Fly Ash
Along with the principal rare earth (REE) minerals such as monazite, xenotime, and bastnasite, Y-and REE-bearing zircon and associated minerals survive the combustion process and are found in coal-combustion fly ash. Beneficiated fly ash from a power plant burning an eastern-Kentucky-sourced coal blend was found to have zircon (ZrSiO4), baddeleyite (ZrO2), fergusonite (YNbO4), yttriaite (Y2O3), and xenotime (YPO4). Previous studies of the same fly had also identified monazite with a broad REE suite. Scanning electron microscopy–electron dispersive spectroscopy (EDS) and transmission electron microscopy (TEM)–EDS as well as other TEM-based techniques revealed a variety of zircon associations, including heavy-REE suites with Y, Nb, and Hf. Hafnium is a common accessory element in zircons and the Y and Nb may be present as fergusonite (YNbO4) intermixed with zircon.
Berti, Debora (ORCID:0000000311237794)↗
Evidence for a High Temperature Whisker Growth Mechanism Active in Tungsten during In Situ Nanopillar Compression
A series of nanopillar compression tests were performed on tungsten as a function of temperature using in situ transmission electron microscopy with localized laser heating. Surface oxidation was observed to form on the pillars and grow in thickness with increasing temperature. Deformation between 850 °C and 1120 °C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y2O3-stabilized ZrO2 indenter. The constraint imposed by the surface oxidation is hypothesized to underly this mechanism for localized plasticity, which is generally the so-called whisker growth mechanism. The results are discussed in context of the tungsten fuzz growth mechanism in He plasma-facing environments. The two processes exhibit similar morphological features and the conditions under which fuzz evolves appear to satisfy the conditions necessary to induce whisker growth.
36 MATERIALS SCIENCE↗
Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures
Systems and methods of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behavior is dependent on interface properties and is attained without cation doping or changes in the gas environment in contact with the sample.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Identifying Challenges in Safeguards for Metallic Fuel Fabrication Facilities
As new advanced reactors gain popularity, there is an increasing interest in metallic fuel fabrication for fast reactors. While metallic fuels themselves are not a new idea, as many of the first reactors employed metallic fuels, new designs, compositions, and fabrication methods are appearing throughout the nuclear community. As the interest grows and facilities are constructed, both domestic and international safeguards will need to be heavily involved to support safeguards-by-design (SBD) measures from the start. This work compiles a review of historical and modern fuel types and fabrication methods, fabrication processes, safeguards gaps, and potential safeguards solutions. Metallic nuclear fuel types have been around for many decades and were included in some of the first reactors including the Experimental Breeder Reactor (EBR)-I and -II, the Fermi 1 reactor, the Integral Fast Reactor (IFR), and the Dounreay Fast Reactor (DFR). These reactors used various compositions including pure uranium (U) metal, U-zirconium (Zr) alloys, plutonium (Pu)-aluminum (Al) alloys, U-fissium (Fs) alloys, U-Pu-Zr alloys, and U-molybdenum (Mo) alloys [1, 2, 3, 4, 5]. These small alloying additions are included to improve the material properties of the pure U metal. The alpha-phase U (stable below 661C) suffers elongation in one direction causing grain boundary cracking and increasing creep rate due to irradiation growth, thermal cycling, and preferential crystal orientation. It is ideal to utilize the gamma-phase U (typically stable above 769C) by adding small amounts of alloying elements such as Zr or Mo to stabilize this phase down to room temperature [3]. Additionally, some research has been focused on U with transuranic (TRU) elements present, typically coming from the used fuel recycling process. Including these elements in fast reactor fuel can aid in the reduction of nuclear waste by burning minor long-lived actinides. However, the additions of TRU elements can cause concerns to arise when trying to fabrication or safeguard metallic fuels. A typical metallic fuel element is shown in Figure 1. Sodium is added into the cladding to create a thermal bond between the fuel slug and cladding wall. The fuel slug is then inserted and the end plug is welded on to the top of the fuel element. A gas plenum is left to create a headspace for gaseous fission products to escape rather than continue to build in the fuel itself [1, 5]. Other fuel element geometries exist as well, such as the Lightbridge twisted cruciform geometry shown in Figure 2 [6]. This design allows for better cooling performance and provides room for fuel rod swelling without impacting the fuel rod diameter. There are many different fabrication methods for metallic fuels, which is one of the many benefits of these fuel types. Many of these fabrication methods are relatively easy and cost-efficient. The most popular fabrication method is injection casting, sometimes called vacuum induction melting (VIM), shown in Figure 3 [4, 8, 9, 7, 10]. This method was largely used for EBR-II fuel fabrication. The injection casting system is contained inside of a vessel consisting of a Y2O3-coated graphite crucible surrounded by an induction coil with ZrO2-coated quartz molds suspended above the crucible. The fuel feedstock is placed inside of the graphite crucible and melted using the induction furnace. The induction furnace utilizes a dual frequency with the high frequency melting the feedstock and the low frequency causing stirring of the melted feedstock to form a homogeneous mixture. The mixture is heated to approximately 1600C in an argon environment. The vessel is evacuated and then the quartz molds are lowered into the graphite crucible containing the molten metal and the vessel is repressurized to inject the metal fuel upwards into the molds. The molds are removed and then shattered to release the fuel slugs. This fabrication method was used to fabricate 39,000 metallic fuel pins for EBR-II. While injection casting has been the most common metallic fuel fabrication method throughout the decades, many other methods have been explored including low-pressure gravity casting, microwave casting, continuous casting, centrifugal casting, coextrusion, and many others [11, 12, 8, 13, 14, 15]. Some of these methods aim to mitigate challenges that arise with americium (Am) volatilization during the casting process for TRU-containing fuel feedstocks, an issue with injection casting. Coextrusion is one of the methods explored at the Idaho National Laboratory (INL) and has been utilized for the initial fabrication tests of Lightbridge's unique fuels, as well as other metallic fuels with cladding coextruded. In this process, large billets are formed and machined and then inserted into a molten salt bath for approximately 30 minutes. The billets are then loaded into the extrusion press and extruded. This process can be seen in Figure 4 [15].
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Fiber Pumped Ho:Sesquioxide Ceramic Materials for Short Pulse Thin disk Lasers (Final Report)
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36 MATERIALS SCIENCE↗
Template-free fabrication of fractal porous Y 2 O 3 monolithic foam and its functional modification by Ni-doping
Fractal structures which display nearly the same character at every scale exist widely in nature, however, it is still a great challenge to fabricate a fractal nanostructure. Herein, a Y 2 O 3 monolith with unique hierarchically fractal porous structure was fabricated via calcination of a fractal porous coordination polymer precursor. The monolith exhibits porous feature with the pore-size ranging from micrometers to nanometers. Interestingly, each level of the pore-wall is composed of secondary porous structures, whose pore-wall is composed of sub-level self-similar porous feature. Moreover, by Ni-doping in the coordination polymer precursor, fractal porous Ni@Y 2 O 3 was prepared, and exhibited enhanced activity in ethanol steam reforming compared with that of a common supported NiO catalyst.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Scaling microstructural processes in the sintering of ionic ceramics
A multi-scale framework, combining a multiphase field formulation and large deformation mechanics, was developed as a stepping stone to perform the data analytics of the microstructural level kinetics of a sintering solid. Relevant microstructural information from this framework, such as grain, stress, and porosity statistics, was scaled up to describe the macroscopic level sintering kinetics. Here, the developed formulation was applied to describe the electric field assisted sintering of Y 2 O 3 . Microstructural inhomogeneities in a multi-granular solid result in the formation of a field of compressive stress networks, which interleave with low compression and weakly tensile regions, defining a scaffolding for sintering concentration regions to develop. A Poisson effect-induced lateral stress network is also naturally self-induced as a result of the mechanical constraints imposed by the sintering apparatus. For long sintering times, localized shear stresses enhancing mass flow along grain boundaries and internal surfaces develop. Three-sided pores are removed by either vacancy transport to the surrounding pores, or move towards the external surfaces through grain boundary diffusion. Four- and higher order-sided pores stabilize because an equal amount of vacancies are gained and lost through the connecting grain boundaries. Grain dewetting contributes to pore coalescence, suggesting that pore kinetics and grain growth are coupled and should be analyzed in concert. The combined sintering and grain growth kinetics define six regimes of sintering behavior: (1) T, the transient regime; (2) E$_Υ$, the surface energy dominated, early sintering regime, where the grain growth exponent, p = 1, and the stress concentration factor, $f$ ~ $1/\hat{ρ}^{4.6}$; (3) E S , the stress dominated, early sintering regime, where p = 1 and $f$ ~ $1/\hat{ρ}^{4}$; (4) I$_Υ$, the surface energy dominated, intermediate sintering regime, where p = 2 and $f$ ~ $1/\hat{ρ}^{4.6}$; (5) I S , the stress dominated, intermediate sintering regime, where p = 2 and $f$ ~ $1/\hat{ρ}^{4}$; and (6) L, the late sintering regime, where p = 3 and $f$ ~ 1. At the macroscopic level, the rapid densification and suppression of grain growth observed in the electric field assisted sintering process is a consequence of the compounding effects of the underlying stress-, transport-, and interfacial-energy-induced energy minimization kinetics, as predicted by the multi-scale framework.
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Synthesis of Nano-Oxide Precipitates by Implantation of Ti, Y and O Ions in Fe-10%Cr: Towards an Understanding of Precipitation in Oxide Dispersion-Strengthened (ODS) Steels
The properties of oxide dispersion-strengthened steels are highly dependent on the nature and size distribution of their constituting nano-oxide precipitates. A fine control of the processes of synthesis would enable the optimization of pertinent properties for use in various energy systems. This control, however, requires knowledge of the precise mechanisms of nucleation and growth of the nanoprecipitates, which are still a matter of debate. In the present study, nano-oxide precipitates were produced via the implantation of Y, Ti, and O ions in two different sequential orders in an Fe-10%Cr matrix that was subsequently thermally annealed. The results show that the oxides that precipitate are not necessarily favoured thermodynamically, but rather result from complex kinetics aspects related to the interaction between the implanted elements and induced defects. When Y is implanted first, the formation of nanoprecipitates with characteristics similar to those in conventionally produced ODS steels, especially with a core/shell structure, is evidenced. In contrast, when implantation starts with Ti, the precipitation of yttria during subsequent high-temperature annealing is totally suppressed, and corundum Cr 2 O 3 precipitates instead. Moreover, the systematic involvement of {110} matrix planes in orientation relationships with the precipitates, independently of the precipitate nature, suggests matrix restriction effects on the early stages of precipitation.
36 MATERIALS SCIENCE↗