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DOE OSTI2016

A solution of the monoenergetic neutral particle transport equation for adjacent half-spaces with anisotropic scattering

We present highly accurate solutions to the neutral particle transport equation in a half-space. While our initial motivation was in response to a recently published solution based on Chandrasekhar's H-function, the presentation to follow has taken on a more comprehensive tone. The solution by H-functions certainly did achieved high accuracy but was limited to isotropic scattering and emission from spatially uniform and linear sources. Moreover, the overly complicated nature of the H-function approach strongly suggests that its extension to anisotropic scattering and general sources is not at all practical. For this reason, an all encompassing theory for the determination of highly precise benchmarks, including anisotropic scattering for a variety of spatial source distributions, is presented for particle transport in a half-space. We illustrate the approach via a collection of cases including tables of 7-place flux benchmarks to guide transport methods developers. The solution presented can be applied to a considerable number of one and two half-space transport problems with variable sources and represents a state-of-the-art benchmark solution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2017

Approximate solutions of acoustic 3D integral equation and their application to seismic modeling and full-waveform inversion

Over the recent decades, a number of fast approximate solutions of Lippmann–Schwinger equation, which are more accurate than classic Born and Rytov approximations, were proposed in the field of electromagnetic modeling. Those developments could be naturally extended to acoustic and elastic fields; however, until recently, they were almost unknown in seismology. This paper presents several solutions of this kind applied to acoustic modeling for both lossy and lossless media. We evaluated the numerical merits of those methods and provide an estimation of their numerical complexity. In our numerical realization we use the matrix-free implementation of the corresponding integral operator. We study the accuracy of those approximate solutions and demonstrate, that the quasi-analytical approximation is more accurate, than the Born approximation. Further, we apply the quasi-analytical approximation to the solution of the inverse problem. It is demonstrated that, this approach improves the estimation of the data gradient, comparing to the Born approximation. The developed inversion algorithm is based on the conjugate-gradient type optimization. Numerical model study demonstrates that the quasi-analytical solution significantly reduces computation time of the seismic full-waveform inversion. We also show how the quasi-analytical approximation can be extended to the case of elastic wavefield.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2021

Multicomponent pyrochlore solid solutions with uranium incorporation – A new perspective of materials design for nuclear applications

Multicomponent pyrochlore solid solutions with and without uranium incorporation were fabricated and their thermal-mechanical properties were characterized. Multicomponent pyrochlore solid solutions without uranium exhibit comparable thermal conductivity and higher mechanical strength compared to baseline single component rare-earth titanate pyrochlore (A 2 Ti 2 O 7 ). Uranium incorporation reduces hardness as compared with single component compositions. High entropy pyrochlore with uranium displays the highest thermal conductivity within multicomponent pyrochlore solid solutions with significantly better mechanical properties than UO 2 . The measured thermal conductivity correlates well with A-site cation mixing entropy and a modified size disorder parameter, and thus the size disorder and mixing entropy could be good indicators for predicting thermal conductivity of multicomponent pyrochlore solid solutions. This work opens up the possibility of designing multicomponent oxide solid solutions by controlling their chemical disorder/mixing entropy to achieve acceptable thermal-mechanical properties, desired radiation and corrosion performance for potential nuclear waste form and inert matrix fuel applications.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2024

A model for trapping and re-solution regarding intra-granular bubbles in UO 2 , linked to atomic-scale simulations

In the literature, a clear definition of the irradiation re-solution frequency of gas from bubbles in the UO 2 fuel is absent. Moreover, for intra-granular bubbles, a detailed calculation of the cumulated displaced gas quantities in function of the distance from the radius of the bubble after a re-solution event has never been published. The assessment of these two elements is very useful if we want to increase the adherence of fission gas release codes to our present knowledge of the behavior of fission gases. Hence, we suggest to link the definition of the re-solution frequency to atomic-scale simulations. Furthermore, we present the cumulated displaced gas quantities obtained from Molecular Dynamics calculations, from which we have derived a re-solution profile that can be exploited to better consider the irradiation re-solution phenomenon inside Fission Gas Release codes. On top of that, we have built a new trapping/re-solution model for intra-granular bubbles linked to Molecular Dynamics simulations that can be easily incorporated into Fission Gas Release codes. In conclusion, we also check that the model is properly built through the comparison of the new model against a reference.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2011

Thick lanthanum zirconate buffer layers from water-based precursor solutions on Ni-5%W substrates

In this work, water-based precursor solutions suitable for dip-coating of thick La{sub 2}Zr{sub 2}O{sub 7} (LZO) buffer layers for coated conductors on Ni-5%W substrates were developed. The solutions were prepared based on chelate chemistry using water as the main solvent. The effect of polymer addition on the maximum crack-free thickness of the deposited films was investigated. This novel solution preparation method revealed the possibility to grow single, crack-free layers with thicknesses ranging 100-280 nm with good crystallinity and an in-plane grain misalignment with average FWHM of 6.55{sup o}. TEM studies illustrated the presence of nanovoids, typical for CSD-LZO films annealed under Ar-5%H{sub 2} gas flow. The appropriate buffer layer action of the film in preventing the Ni diffusion was studied using XPS. It was found that the Ni diffusion was restricted to the first 30 nm of a 140 nm thick film. The surface texture of the film was improved using a seed layer. - Graphical abstract: Thick LZO buffer layers from water-based precursor solutions were synthesized and their crystallinity, microstructure and buffer layer action were studied. The buffer layer action of the LZO layer was substantial to restrict the Ni penetration within 30 nm of a 140 nm thick film. Highlights: > LZO buffer layers with high thicknesses for use in coated conductors were prepared. > Prepared from water-based solutions. > Polymeric PVP increases the crack-free critical thickness of thick films. > Thick films showed good barrier action against Ni penetration. > Seed layers promote epitaxial growth of thick layers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2012

NaCu(Ta{sub 1-y}Nb{sub y}){sub 4}O{sub 11} solid solution: A tunable band gap spanning the visible-light wavelengths

The new solid-solution NaCu(Ta{sub 1-y}Nb{sub y}){sub 4}O{sub 11} (0{<=}y{<=}0.7) was synthesized by solid-state methods in the form of bulk powders that ranged from light-yellow to brown colored and were characterized by powder X-ray diffraction techniques (Space group R-3c (no. 167); Z=6; a=6.214(1)-6.218(1) Angstrom-Sign and c=36.86(1)-36.94(1) Angstrom-Sign ). Full-profile Rietveld refinements confirmed a site-differentiated ordering of the Cu(I) and Na cations, i.e., occupying the 12c (linear environment) and 18d (seven-coordinate environment) crystallographic sites respectively. Conversely, a statistical mixture of Ta(V) and Nb(V) cations occurred over the 6b (octahedral environment) or the 18e (pentagonal-bipyramidal environment) crystallographic sites, without any preferential segregation. The UV-Vis diffuse reflectance spectra showed a significant red-shift of the optical bandgap size (indirect) from {approx}2.70 eV to {approx}1.80 eV across the solid solution with increasing Nb(V) content. Electronic-structure calculations using the tight-binding linear-muffin-tin-orbital approach showed that the reduction in bandgap size arises from the introduction of the lower-energy Nb 4d{sup 0} orbitals into the conduction band and consequently a lower energy of the conduction band edge. The lowest-energy bandgap transitions were found to be derived from electronic transitions between the filled Cu(I) and the empty Nb(V) d-orbitals, with a small amount of mixing with the O 2p orbitals. The resulting conduction and valence band energies are found to approximately bracket the redox potentials for water reduction and oxidation, and meeting the thermodynamic requirements for photocatalytic water-splitting reactions. - Graphical Abstract: The NaCu(Ta{sub 1-y}Nb{sub y}){sub 4}O{sub 11} (0{<=}y{<=}0.7) solid solution shows a statistical occupancy of the Ta(V) and Nb(V) cations in both octahedral and pentagonal bipyramidal environments. An increasing Nb(V) content also causes a significant red-shift of the bandgap size from {approx}2.70 eV to {approx}1.80 eV. Highlights: Black-Right-Pointing-Pointer Double solid-solution of M(I) (=Cu, Na) and M(V) (=Nb, Ta) crystallographic sites. Black-Right-Pointing-Pointer Increasing Nb content leads to tunable bandgap size from {approx}2.70 eV to {approx}1.80 eV across the solid solution. Black-Right-Pointing-Pointer Layers of MO{sub 7} (M=Ta, Nb) pentagonal bipyramids and isolated MO{sub 6} octahedra.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4}: Novel keesterite type solid solutions

A new family of Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} chalcogenides has been synthesized by conventional solid-state reactions at 850 Degree-Sign C. The reactions products were characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray analysis (SEM-EDS), Raman spectroscopy and magnetic susceptibility. The crystal structures of two members of the solid solution series Cu{sub 2}Mn{sub 0.4}Co{sub 0.6}SnS{sub 4} and Cu{sub 2}Mn{sub 0.2}Co{sub 0.8}SnS{sub 4} have been determined by single-crystal X-ray diffraction. Both phases crystallize in the tetragonal keesterite-type structure (space group I4{sup Macron }). The distortions of the tetrahedral volume of Cu{sub 2}Mn{sub 0.4}Co{sub 0.6}SnS{sub 4} and Cu{sub 2}Mn{sub 0.2}Co{sub 0.8}SnS{sub 4} were calculated and compared with the corresponding differences in the Cu{sub 2}MnSnS{sub 4} (stannite-type) end-member. The compounds show nearly the same Raman spectral features. Temperature-dependent magnetization measurements (ZFC/FC) and high-temperature susceptibility indicate that these solid solutions are antiferromagnetic. - Graphical abstract: View along [100] of the Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} structure showing tetrahedral units and magnetic measurement ZFC-FC at 500 Oe. The insert shows the 1/{chi}-versus-temperature plot fitted by a Curie-Weiss law. Highlights: Black-Right-Pointing-Pointer Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} solid solutions belong to the family of compounds adamantine. Black-Right-Pointing-Pointer Resolved single crystals of the solid solutions have space group I4{sup Macron }. Black-Right-Pointing-Pointer The distortion of the tetrahedral volume of Cu{sub 2}Mn{sub 1-x}Co{sub x}SnS{sub 4} were calculated. Black-Right-Pointing-Pointer These solid solutions are antiferromagnetic.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Structural studies of TiC{sub 1−x}O{sub x} solid solution by Rietveld refinement and first-principles calculations

The lattice parameters, structural stability and electronic structure of titanium oxycarbides (TiC{sub 1−x}O{sub x}, 0≤x≤1) solid solution were investigated by Rietveld refinement and first-principles calculations. Series of TiC{sub 1−x}O{sub x} were precisely synthesized by sintering process under the vacuum. Rietveld refinement results of XRD patterns show the properties of continuous solid solution in TiC{sub 1−x}O{sub x} over the whole composition range. The lattice parameters vary from 0.4324 nm to 0.4194 nm decreasing with increasing oxygen concentration. Results of first-principles calculations reveal that the disorder C/O structure is stable than the order C/O structure. Further investigations of the vacancy in Ti{sub 1−Va}(C{sub 1−x}O{sub x}){sub 1−Va} solid solution present that the structure of vacancy segregated in TiO-part is more stable than the disorder C/O structure, which can be ascribed to the Ti–Ti bond across O-vacancy and the charge redistributed around Ti-vacancy via the analysis of the electron density difference plots and PDOS. - Graphical abstract: XRD of series of titanium oxycarbides (TiC{sub 1−x}O{sub x}, 0≤x≤1) solid solution prepared by adjusting the proportion of TiO in the starting material. Highlights: • Titanium oxycarbides were obtained by sintering TiO and TiC under carefully controlled conditions. • Rietveld refinement results show continuous solid solution with FCC structure in TiC{sub 1−x}O{sub x}. • The disorder C/O structure is stable than the order C/O structure. • Introduction of vacancy segregated in TiO-part is more stable than disorder C/O structure. • Ti–Ti bond across O-vacancy and the charge redistributed around Ti-vacancy enhance structural stability.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Synthesis of finely divided molybdenum sulfide nanoparticles in propylene carbonate solution

Molybdenum sulfide nanoparticles have been prepared from the reflux solution reaction involving ammonium heptamolybdate and elemental sulfur in propylene carbonate. Addition to the reaction mixture of starch as a natural capping agent leads to lesser agglomeration and smaller size of the particles. Nanoparticles of MoS{sub x} (x≈4) of 10–30 nm size are highly divided and form stable colloidal suspensions in organic solvents. Mo K edge EXAFS of the amorphous materials shows rapid exchange of oxygen to sulfur in the molybdenum coordination sphere during the solution reaction. Thermal treatment of the amorphous sulfides MoS{sub x} under nitrogen or hydrogen flow at 400 °C allows obtaining mesoporous MoS{sub 2} materials with very high pore volume and specific surface area, up to 0.45 cm{sup 3}/g and 190 m{sup 2}/g, respectively. The new materials show good potential for the application as unsupported hydrotreating catalysts. - Graphical abstract: Solution reaction in propylene carbonate allows preparing weakly agglomerated molybdenum sulfide with particle size 20 nm and advantageous catalytic properties. - Highlights: • Solution reaction in propylene carbonate yields MoS{sub x} particles near 20 nm size. • Addition of starch as capping agent reduces particles size and hinder agglomeration. • EXAFS at Mo K edge shows rapid oxygen to sulfur exchange in the solution. • Thermal treatment leads to MoS{sub 2} with very high porosity and surface area.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Ab initio calculation of excess properties of La{sub 1−x}(Ln,An){sub x}PO{sub 4} solid solutions

We used ab initio computational approach to predict the excess enthalpy of mixing and the corresponding regular/subregular model parameters for La{sub 1−x}Ln{sub x}PO{sub 4} (Ln=Ce,…, Tb) and La{sub 1−x}An{sub x}PO{sub 4} (An=Pu, Am and Cm) monazite-type solid solutions. We found that the regular model interaction parameter W computed for La{sub 1−x}Ln{sub x}PO{sub 4} solid solutions matches the few existing experimental data. Within the lanthanide series W increases quadratically with the volume mismatch between LaPO{sub 4} and LnPO{sub 4} endmembers (ΔV=V{sub LaPO{sub 4}}−V{sub LnPO{sub 4}}), so that W(kJ/mol)=0.618(ΔV(cm{sup 3}/mol)){sup 2}. We demonstrate that this relationship also fits the interaction parameters computed for La{sub 1−x}An{sub x}PO{sub 4} solid solutions. This shows that lanthanides can be used as surrogates for investigation of the thermodynamic mixing properties of actinide-bearing solid solutions. - Highlights: • The excess enthalpies of mixing for monazite-type solid solutions are computed. • The excess enthalpies increase with the endmembers volume mismatch. • The relationship derived for lanthanides is transferable to La{sub 1−x}An{sub x}PO{sub 4} systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Mechanosynthesis and structural characterization of nanocrystalline Ce{sub 1–x}Y{sub x}O{sub 2–δ} (x=0.1–0.35) solid solutions

A series of nanostructured fluorite-type Ce{sub 1–x}Y{sub x}O{sub 2–δ} (0≤x≤0.35) solid solutions, prepared via high-energy milling of the CeO{sub 2}/Y{sub 2}O{sub 3} mixtures, are investigated by XRD, HR-TEM, EDS and Raman spectroscopy. For the first time, complementary information on both the long-range and short-range structural features of mechanosynthesized Ce{sub 1–x}Y{sub x}O{sub 2–δ}, obtained by Rietveld analysis of XRD data and Raman spectroscopy, is provided. The lattice parameters of the as-prepared solid solutions decrease with increasing yttrium content. Rietveld refinements of the XRD data reveal increase in microstrains in the host ceria lattice as a consequence of yttrium incorporation. Raman spectra are directly affected by the presence of oxygen vacancies; their existence is evidenced by the presence of vibration modes at ~560 and ~600 cm{sup –1}. The detailed spectroscopic investigations enable us to separate extrinsic and intrinsic origin of oxygen vacancies. It is demonstrated that mechanosynthesis can be successfully employed in the one-step preparation of nanocrystalline Ce{sub 1–x}Y{sub x}O{sub 2–δ} solid solutions. - Graphical abstract: Mechanosynthesis of nanocrystalline Ce{sub 1–x}Y{sub x}O{sub 2–δ} (x=0.1–0.35) solid solutions. - Highlights: • One-step mechanosynthesis of nanoscale Ce{sub 1–x}Y{sub x}O{sub 2–δ} (0≤x≤0.35) solid solutions. • Complementary information on the long-range and short-range structural features of mechanosynthesized Ce{sub 1–x}Y{sub x}O{sub 2–δ} is provided. • Structural variations as a response to the yttrium doping. • Separation of extrinsic and intrinsic origin of the induced oxygen vacancies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

HT-solution growth and characterisation of In{sub x}Na{sub x}Mn{sub 1-2x}WO{sub 4} (0<x≤0.26)

A new solid solution system, In{sub x}Na{sub x}Mn{sub 1–2x}WO{sub 4} (0<x=≤0.26) belonging to the MnWO{sub 4}-type multiferroics was investigated. Large single crystals were grown up to several mm in length from high-temperature oxide solutions using a solvent mixture of Na{sub 2}WO{sub 4} and Na{sub 2}W{sub 2}O{sub 7}. Quantitative doping degrees were analyzed by means of electron microprobe. Single crystal X-ray diffraction studies agreed with the polar space group P2 for In{sub x}Na{sub x}Mn{sub 1–2x}WO{sub 4}. The complexity of partial (Na{sup +}/Mn{sup 2+})- and (In{sup 3+}/Mn{sup 2+})-ordering makes their atomic sites unique, explaining the dissymmetrization from P2/c down to P2. This is also valid for the InNaW{sub 2}O{sub 8}-type Mn{sub 2y}In{sub 1-y}Na{sub 1-y}W{sub 2}O{sub 8} solid solution found as co-product in this study. Specific heat and magnetisation measurements showed a paramagnetic dilution effect from (In{sup 3+}/Na{sup +})-doping while lowering the transition temperature for the multiferroic phase AF2 of In{sub x}Na{sub x}Mn{sub 1–2x}WO{sub 4} with respect to the prototype MnWO{sub 4}. - Graphical abstract: A volume expansion around Mn2 site by (In, Na)-doping is drawn by the atomic shifts in a Mn2O{sub 6} octahedron in the atomistic structure of In{sub 0.20(2)}Na{sub 0.17(2)}Mn{sub 0.63(4)}WO{sub 4} from the respective atomic positions of In-free MnWO{sub 4}. The size and direction of arrows are scaled up for indicating the consequent local distortion. - Highlights: • HT solution crystal growth of (In, Na):MnWO{sub 4}-solid-solution compounds. • Polar space group symmetry P2 for their atomistic structures. • Magnetic properties of the multiferroic phase AF2 by (In{sup 3+}, Na{sup +})-doping. • Magnetic phase transitions.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Characterization of Cu–Ni nanostructured alloys obtained by a chemical route. Influence of the complexing agent content in the starting solution

The influence of the amount of complexing agent added to the starting solution on the physicochemical properties of Cu–Ni nanostructured alloys obtained through a chemical route, was studied. For this purpose, three Cu–Ni nanoalloy samples were synthesized by a previously developed procedure, starting from solutions with citric acid to metal molar ratios (C/Me) of 0.73, 1.00 and 1.50. The synthesis technique consisted in preparing a precursor via the citrate-gel method, and carrying out subsequent thermal treatments in controlled atmospheres. Sample characterization was performed by scanning electron microscopy, X-ray microanalysis, X-ray diffraction, transmission electron microscopy, X-ray nanoanalysis and electron diffraction. In the three cases, copper and nickel formed a solid solution with a Cu/Ni atomic ratio close to 50/50, and free of impurities inside the crystal structure. The citric acid content of the starting solution proved to have an important influence on the morphology, size distribution, porosity, and crystallinity of the Cu–Ni alloy microparticles obtained, but a lesser influence on their chemical composition. The molar ratio C/Me = 1.00 resulted in the alloy with the Cu/Ni atomic ratio closest to 50/50. - Highlights: • We synthesize Cu–Ni nanoalloys by a chemical route based on the citrate-gel method. • We study the influence of the complexing agent content of the starting solution. • We characterize the samples by electron microscopy and X-ray techniques. • Citric acid influences the shape, size, porosity and crystallinity of the alloys.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Fabrication of Al-Zn solid solution via friction stir processing

Highlights: • Thermomechanical nature of FSP was utilized for mechanical alloying. • Zn particles dissolved in Al during FSP to form solid solution. • Second pass of FSP lead to homogenization and partial decomposition of the solid solution. • Processed alloy exhibited improved hardness over base and FSPed metal. • The process can be adopted for site specific property enhancement. - Abstract: The present study demonstrates that friction stir processing (FSP) can be used as a mechanical alloying tool to process solid solution. Zn was incorporated in commercially pure aluminium by multi-pass FSP leading to its dissolution and formation of supersaturated solid solution which was confirmed by X-ray diffraction and scanning electron microscopy. The hardness across the stir zone matched with the distribution of Zn and was significantly improved compared to the base metal. The supersaturated solid solution that formed in the first pass, partially decomposed during the second pass, leading to the formation of fine Al-Zn precipitates. Thermal stability of the microstructure against abnormal grain growth was also improved after the second pass due to the pinning effect of the grain boundary precipitates. FSP also caused grain refinement of the alloy yielding fine equiaxed grains in the range of 4–6 μm with a high fraction (> 67%) of high angle grain boundaries. Such microstructure is conducive for isotropic properties and the fact that the microstructure is stable against thermal cycles make the process suitable for selective alloying for location specific property enhancement.

36 MATERIALS SCIENCE↗

DOE OSTI2011

The magnetic properties of Bi{sub 0.9}Ba{sub 0.1}Fe{sub 0.81}M{sub 0.09}Ti{sub 0.1}O{sub 3} solid solutions (M = Co, Mn, Sc, Al)

Graphical abstract: In Bi{sub 0.9}Ba{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} solid solution, both magnetic ions (Co{sup 3+}, Mn{sup 3+}) and nonmagnetic ions (Sc{sup 3+}, Al{sup 3+}) were chosen to partially replace Fe{sup 3+}. Their magnetic properties were carefully investigated. Figures show M-H loops at RT of Co{sup 3+} doped sample (left) and Sc{sup 3+} substituted solid solution (right). Highlights: {yields} The electrical resistivity of BiFeO{sub 3} is enhanced by forming solid solution with BaTiO{sub 3}. {yields} We replace Fe{sup 3+} by both magnetic ions Co{sup 3+}, Mn{sup 4+} and nonmagnetic ions Sc{sup 3+}, Al{sup 3+} to investigate the magnetic properties. {yields} Structure-magnetic property relationship has been established by Rietveld refinement. -- Abstract: Solid solutions with general formula Bi{sub 0.9}Ba{sub 0.1}Fe{sub 0.81}M{sub 0.09}Ti{sub 0.1}O{sub 3} (M = Co, Mn, Sc, Al) together with parental Bi{sub 0.9}Ba{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} were prepared by the traditional solid state reaction method. Their structural, room temperature magnetic, and dielectric properties were investigated. X-ray diffraction analysis indicated that all samples maintained original R3c space group. M-H hysteresis loop of Co{sup 3+} doped sample saturated at an applied field of 1 T with spontaneous magnetization of 1.735 emu/g, while Mn{sup 4+} substitution enhanced the magnetization of Bi{sub 0.9}Ba{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} less strongly; addition of Sc{sup 3+} helped decrease magnetic coercive field while Al{sup 3+} modified sample exhibited paramagnetic M-H hysteresis loop. Differential scanning calorimetry was applied to determine the Neel temperature (T{sub N}) and the T{sub N} for undoped, Co{sup 3+}, Mn{sup 4+}, Sc{sup 3+}, Al{sup 3+} doped solid solutions were 318.1, 324.3, 335.7, 293.9 and 295.8 respectively. Sc{sup 3+} substitution had little influence on the dielectric properties of Bi{sub 0.9}Ba{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} while Al{sup 3+} doping improved its dielectric constant. In contrast, Co{sup 3+}, Mn{sup 4+} doped samples showed decreased permittivity but inhibited tan {delta} at frequencies larger than 30 kHz.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Thermal decomposition behavior of Cu–Al layered double hydroxide, and ethylenediaminetetraacetate-intercalated Cu–Al layered double hydroxide reconstructed from Cu–Al oxide for uptake of Y{sup 3+} from aqueous solution

Graphical abstract: Display Omitted Highlights: ► Decomposition of CO{sub 3}·Cu–Al LDH occurred in four stages. ► The edta·Cu–Al LDH was found to take up Y{sup 3+} in aqueous solution. ► The edta·Cu–Al LDH could selectively take up rare earth ions from a mixed solution. -- Abstract: CO{sub 3}{sup 2−}-intercalated Cu–Al layered double hydroxide (CO{sub 3}·Cu–Al LDH) was calcined to yield Cu–Al oxide, and then ethylenediaminetetraacetate-intercalated Cu–Al LDH (edta·Cu–Al LDH) was prepared by reconstructing Cu–Al oxide in edta solution. Decomposition of CO{sub 3}·Cu–Al LDH occurred in four stages. The production of Cu–Al oxide was caused by the thermal decomposition of CO{sub 3}·Cu–Al LDH until the third stage. The first stage was the elimination of adsorbed surface water and interlayer water in CO{sub 3}·Cu–Al LDH. The second and third stages were the dehydroxylation of the brucite-like octahedral layers and the elimination of CO{sub 3}{sup 2−} intercalated in the interlayers. The edta·Cu–Al LDH was found to take up Y{sup 3+} in aqueous solution. The uptake of Y{sup 3+} was caused not only by the chelating function of Hedta{sup 3−} in the interlayer but also by the chemical behavior of Cu–Al LDH itself. The edta·Cu–Al LDH was found to selectively take up rare earth ions from a mixed solution. The degree of uptake was high, in the order Sc{sup 3+} > Y{sup 3+} > La{sup 3+} for all time durations, which was attributable to differences among the stabilities of Sc(edta){sup −}, Y(edta){sup −} and La(edta){sup −}.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Water-dispersible and quasi-superparamagnetic magnetite nanoparticles prepared in a weakly basic solution at the low synthetic temperature

Highlights: • Magnetite nanoparticles were prepared in a weakly basic solution at the low reaction temperature. • The double layer may be steadily formed on the surfaces of magnetite nanoparticles at the high pH value. • Magnetite nanoparticles present a quasi-superparamagnetic property and a good dispersion in the aqueous solution. - Abstract: Magnetite nanoparticles were prepared in a weakly basic solution at the low reaction temperature by the co-precipitation method. As a comparison, the oxidative precipitation method was also applied in this study. The structure, morphology, and other properties of the obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The above characterization data indicate that small size and narrow size distribution are found for magnetite nanoparticles prepared by the co-precipitation method. Further magnetic property and Zeta potential results illuminate that magnetite nanoparticles prepared by this method display a quasi-superparamagnetic property and a good dispersion in the aqueous solution. Based on the investigation results, the magnetite nanoparticles with a quasi-superparamagnetic property and a fine dispersion can be facilely prepared in a weakly basic solution at the low reaction temperature by the co-precipitation method.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2025

The role of excess vacancies in stabilizing solute clusters in low-alloy steels

The formation of solute clusters in irradiated low-alloy steels, such as reactor pressure vessel steels, is a critical cause of radiation hardening and embrittlement. However, the chemical interactions among solute elements and excess vacancies remain to be fully understood. This study employs density functional theory, cluster expansion, and lattice-based Monte Carlo simulations to examine the stability and morphology of nano-size coherent solute clusters with excess vacancies. The findings reveal that excess vacancies are crucial in stabilizing and promoting the growth of Mn-Ni-Si-vacancy clusters. A minimum of seven vacancies is required for stable nucleation and growth of these clusters. These Mn-Ni-Si clusters act as defect sinks, effectively trapping and absorbing mobile vacancies generated under irradiation. Furthermore, phosphorus (P) preferentially dissolves in Mn-Ni-Si clusters due to chemical coupling with vacancies. In conclusion, this study offers new insights into solute-vacancy interactions, enhancing our understanding of solute-defect cluster formation and embrittlement in low-alloy steels.

36 - MATERIALS SCIENCE↗