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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Zinc oxide based sorbent and process for preparing same

Zinc oxide-based sorbents, and processes for preparing and using them are provided, wherein the sorbents are preferably used to remove one or more reduced sulfur species from gas streams. The sorbents contain an active zinc component, optionally in combination with one or more promoter components and/or one or more substantially inert components. The active zinc component is a two-phase material, consisting essentially of a zinc oxide (ZnO) phase and a zinc aluminate (ZnAl 2 O 4 ) phase. Each of the two phases is characterized by a relatively small crystallite size of typically less than about 50 nm (500 Angstroms). Preferably the sorbents are prepared by using an alkali metal base to convert a precursor mixture, containing a precipitated zinc oxide precursor and a precipitated aluminum oxide precursor, to the two-phase, active zinc oxide containing component, with the resulting sorbent having a sodium level within a desired range.

Shen, Jian-Ping↗
DOE OSTI2023

Thermal barrier coatings

High temperature stable thermal barrier coatings useful for substrates that form component parts of engines such as a component from a gas turbine engine exposed to high temperatures are provided. The thermal barrier coatings include a multiphase composite and/or a multilayer coating comprised of two or more phases with at least one phase providing a low thermal conductivity and at least one phase providing mechanical and erosion durability. Such low thermal conductivity phase can include a rare earth zirconate and such mechanical durability phase can include a rare earth a rare earth aluminate. The different phases are thermochemically compatible even at high temperatures above about 1200° C.

Wolfe, Douglas E.↗
DOE OSTI2019

Robust and High-Waste Loaded Glass Formulations for Hanford Low-Activity Waste - 19050

The Hanford Low-Activity Waste (LAW) vitrification facility will receive LAW batches with abruptly changing compositions that span relatively broad ranges. In particular, the concentration ratios of sodium-to-sulfate, -chloride, -chromate, -phosphate, -potassium, and -aluminate create challenges in glass formulation. Glass compositions that simultaneously satisfy several processability, product quality, and composition constraints with sufficient confidence must be formulated for each LAW batch in near-realtime to enable desired throughput. A method for developing glass compositions while maximizing the waste loading and the process robustness was developed. This method compiled the glass composition-property data collected over nearly two decades, primarily by Pacific Northwest National Laboratory, The Catholic University of America, and Savannah River National Laboratory, in support of both the Hanford Tank Waste Treatment and Immobilization Plant project and the U.S. Department of Energy Office of River Protection Enhanced Waste Glass project. These data were used to develop models that link the melter feed composition to the resulting glass properties. Mathematical constructs were developed to optimize glass compositions for each waste batch in real-time that will simultaneously satisfy processability, product quality, and composition constraints with sufficient statistical confidence. Property prediction and various process uncertainties were reflected in the formulation. The formulation approach directly lends itself to adjustment of glass formulation to achieve program goals. This presentation will summarize the formulation approach and supporting data. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

3D Printable Polymers for Radiological Applications

Additive manufacturing of polymers is a widely used and growing technology throughout the DOE complex. Composite filaments for Fused Deposition Modeling (FDM) printers are commonly used to enhance material properties such as mechanical strength, operating temperature and chemical resistance. Radio luminescent properties were added to 3D filaments by impregnating clear poly(ethylene terephthalate)-glycol (PETG) with X-ray scintillator powder. X-ray scintillators have unique, narrow emission spectra which can be imaged with low light DSLR cameras, photomultiplier tubes, or spectrometers. Filament Production: 1. Pellets are loaded into the hopper. 2. Temperature and extrusion speed are set on extruder. 3. Extruder turned on and filament is pulled from nozzle along air path to cool. 4. Spooler drive speeds set. 5. Filament is inserted through Filameasure then guided along drive wheels and into traverse. 6. Parameters adjusted to obtain 1.75 mm diameter 7. Filament is inserted into spooler wheel. Traverse speed set and slip nut adjusted to make tight and even roll. From Raw Materials to Printed Part: Clear PETG pellets were dipped in ZnS:Cu scintillator powder to coat pellets. Coated and uncoated pellets were mixed together before inserting into hopper. Filament showed trace amounts of powder and luminesced under UV light. Powder distribution is random and not reproducible thus providing a unique identification marker potentially useful for national security applications. Multiple X-ray scintillators can be arranged in a panel to discriminate incident X-ray photon energies. Variable panel arrangement: pixelated, layered, solid from homogenous filament. Ratio of emission intensities. Response varies with incident photon energy. Spectrally separate scintillators. Scintillators: Yttrium Oxide Europium Doped - Red, Gadolinium Oxysulfide Terbium Doped - Green, Barium Magnesium Aluminate Europium Doped - Blue, Zinc Sulfide Copper Doped - Green. Powder concentrations will need to be increased in the filament for use in the energy discriminating panel. Homogeneity in the filament will be a challenge that can be solved by turning the pellets into a powder and mixing it with scintillator powder prior to extrusion. The panels will be tested using x-ray booths and button sources such as Am-241, Cs-137, and Co-60.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Super-hydrophobic, thermally insulating, thermal-shocks resistant well cement composites for completion of geothermal wells at hydrothermal temperatures of up to 300° C

A well cement composite and a method for making a well cement composite includes a mixture of calcium aluminate cement (CAC) and fly ash cenospheres (CS) in a weight ratio of from 30:70 to 80:20 CAC to CS; sodium metasilicate (SMS) in an amount of from 1 to 10% of the total weight of the mixture of CAC and CS; polymethylhydrosiloxane (PMHS) in an amount of from 0.5 to 6.0% of the total weight of the mixture of CAC and CS; and water in a weight ratio of from 0.5:1.0 to 1.2:1.0 of water to CAC and CS.

Pyatina, Tatiana↗
DOE OSTI2017

Luminescence of Eu:Y{sub 3}Al{sub 5}O{sub 12}, Eu:Lu{sub 3}Al{sub 5}O{sub 12}, and Eu:GdAlO{sub 3} Nanocrystals Synthesized by Solution Combustion

Nanocrystals of rare-earth garnets Y{sub 3}Al{sub 5}O{sub 12} and Lu{sub 3}Al{sub 5}O{sub 12} and perovskite GdAlO{sub 3} highly doped (10–20 at%) with Eu{sup 3+} are synthesized by the solution combustion technique and subsequent annealing in air at 800 and 1300{sup o}C. Their structure, morphology, and phase composition are studied. These materials exhibit intense red luminescence under UV excitation. Eu:GdAlO{sub 3} luminescence has CIE 1931 color coordinates (0.632, 0.368); dominant wavelength, 599.6 nm; and color purity, >99%. Judd–Ofelt parameters, luminescence branching ratios, and lifetimes of the Eu{sup 3+5}D{sub 0} state are determined. The luminescence quantum yield for Eu:GdAlO{sub 3} (10 at%) reaches 74% with a lifetime of 1.4 ms for the {sup 5}D{sub 0} state. The synthesized materials are promising for red ceramic phosphors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Study of Electrical Transport and Magnetic Properties of Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3}/Nd{sub 0.8}Na{sub 0.2}MnO{sub 3} Bilayer Thin Films

Bilayer films of Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3}/Nd{sub 0.8}Na{sub 0.2} MnO{sub 3} were grown on 001-orientated LaAlO{sub 3} substrate by using RF magnetron sputtering. The thickness of the Nd{sub 0.8}Na{sub 0.2}MnO{sub 3} (NNMO) film was kept fixed at 120 nm while that of the Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3} (NSMO) film was varied from 12 to 100 nm. X-ray diffraction patterns confirm the growth of films along the (001) direction, and the out-of-plane lattice constant of the NSMO film decreases with an increase in film thickness. The bilayer films are found to undergo out-of-plane tensile strain, and the lattice strain is found to decrease with an increase in film thickness. The ferromagnetic transition temperature is found to increase with an increase in the NSMO film thickness. M–H loops recorded at 50 K show a systematic increase in saturation magnetisation with an increase in film thickness. Metal–insulator transition has been observed for the film thickness of 30 nm and above, and the transition temperature is found to increase with an increase in film thickness. The electrical resistivity data in the metallic region were explained based on electron–electron and electron–magnon scattering mechanism by including a weak localisation effect at low temperature. The electrical resistivity data in the insulating region follow the Mott-variable range hopping model.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Investigation on the Current Transport Characteristics of SrTiO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7−x} Heterostructure

By the combined use of the sol-gel and pulsed laser deposition methods, the SrTiO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7−x} (STO/YBCO) heterostructure was prepared on a LaAlO{sub 3} substrate. XRD results and φ scanning test showed that the prepared STO/YBCO heterostructure had good biaxial texture. Moreover, a Pt electrode was sputtered on the STO/YBCO heterostructure to investigate the current density-voltage (J − V) characteristic curves of STO/YBCO in the 50–300 K temperature range. The results showed that the STO/YBCO heterostructure had good rectifying characteristics. With an applied positive bias voltage smaller than 3.7 V, the current density of the STO/YBCO heterostructure decreased with the decrease of temperature; for higher voltages, on the contrary, the current density increased with the decrease of temperature. When the YBCO experienced superconducting transition, the turn-on voltage (V{sub t}) changed suddenly due to the sudden opening of the superconducting energy gap of YBCO. The V{sub t} variation obtained from the experiment was essentially consistent with the known value of the YBCO superconducting energy gap.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Yb Substitution on Microstructure and Superconducting Properties of Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} Films

The purpose of this study was to improve the critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) superconducting films at high magnetic fields. Thin Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} (Y{sub 1−x}Yb{sub x}BCO) superconducting films on LaAlO{sub 3} substrates were prepared by modified low-fluorine metal organic deposition method (LF-MOD) in order to investigate the effect of Yb substitution on the microstructure and superconducting properties of a YBCO-coated conductor. In this study, single-phased, c-axial-aligned Y{sub 1−x}Yb{sub x}BCO films were obtained. Yb doping had a little effect on the critical temperature (T{sub c}) and transition width (ΔT) values of Y{sub 1−x}Yb{sub x}BCO films. An abnormal phenomenon was observed that the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at low field was smaller than that of the pure YBCO film, but the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at high field was much greater than that of the undoped YBCO film. Compared to pure YBCO film, the J{sub c} values of Y{sub 0.75}Yb{sub 0.25}BCO and Y{sub 0.25}Yb{sub 0.75}BCO films were enhanced by a factor of 8 at 8 T, 65 K, which meant that chemical substitution of Yb into the Y site could improve flux pinning significantly under the high magnetic field in Y{sub 1−x}Yb{sub x}BCO coated conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Evolution of Intrinsic and Magnetic Field-Induced Magnetic Anisotropies in Strongly Phase-Separated Manganite Thin Films

Single crystalline thin film (∼ 100 nm) of La{sub 0.18}Pr{sub 0.40}Ca{sub 0.42}MnO{sub 3} is grown on (001) oriented LaAlO{sub 3} substrates and the evolution of anisotropy associated with the supercooling behaviour of the magnetic liquid is studied as a function of temperature and magnetic field. The angle-dependent magnetization measurements ascertain that the easy magnetic axis lies in the plane of the film while the hard axis is along the plane normal. The ratio of the easy and hard axes magnetizations (M{sub ||} and M{sub ⊥}) measured at 10 K, viz., M{sub ||}/M{sub ⊥} (10 K) = 2.6, confirms the strongly anisotropic nature of the film. The easy axis ferromagnetic (FM) transition temperature (T{sub C}) is smaller than that along the hard axis. The giant hysteresis in FCC–FCW M–T, which manifests the magnetic liquid behaviour of the strongly phase-separated manganites is appreciably narrowed along the hard axis. The strain glass state is also less dominant along the easy axis. The analysis of the M–H data brings out that the easy axis remanence (M{sub r||}) shows a nonlinear temperature dependence, while the one corresponding to the hard axis (M{sub r⊥}) shows a nearly linear behaviour. The coercivity (H{sub C}) follows a law of the type H{sub C}(T)=H{sub C}(0)(1−AT{sup b}). The value of exponent b ∼ 0.5 for single-domain particles, but in the present case, the best fit to the experimental data yields the exponent b ≈ 0.25 for both H{sub C||} and H{sub C⊥}. The smaller value of the exponent is attributed to the non-canonical nature of the ferromagnetic state and the associated strongly phase-separated nature of the LPCMO thin film.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Modulation of Superconducting Transition Temperature in LaAlO{sub 3}/SrTiO{sub 3} by SrTiO{sub 3} Structural Domains

The tetragonal domain structure in SrTiO{sub 3} (STO) is known to modulate the normal-state carrier density in LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) heterostructures, among other electronic properties, but the effect of STO domains on the superconductivity in LAO/STO has not been fully explored. Using a scanning SQUID susceptometer microscope to map the superconducting response as a function of temperature in LAO/STO, we find that the superconducting transition temperature is spatially inhomogeneous and modulated in a pattern that is characteristic of structural domains in the STO.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

A chemical/mineralogical investigation of the behavior of sulfoaluminate binders submitted to accelerated carbonation

The paper addresses the carbonation of CSA based binders from the mechanical, chemical and mineralogical point of view. Three different binders have been investigated, revealing that many hydrated phases can protect ettringite against carbonation. In particular, the presence of AFm phases gives a significant contribution to buffer the pH in alkaline range and to preserve the protective film of steel reinforcement bars. In a carbonated environment AFm phases act as ionic exchangers: carbonate ions replace sulfates in the interlayer and in these conditions the released sulfate ions contribute to the formation of new ettringite, with a beneficial effect on compressive strength performances. Experimental data are compared with models and carbonation mechanisms are described.

36 MATERIALS SCIENCE↗
DOE OSTI2021

An insight on the effect of sodium and silicon on microstructure and crystallography of high alumina cements

In the present study the influence of minor elements (Na{sub 2}O and SiO{sub 2}) on the mineralogy, chemistry and microstructure of High Alumina Cements (HACs) has been investigated. HACs have several advantages respected to Ordinary Portland Cement (OPC) but the shortage of Al-rich raw materials represents a limiting factor: re-use of Al-rich waste as raw material represents a solution but it will add minor elements to the raw meal that could change HACs properties. For the first time, four commercial HACs, doped with sodium and silicon, and one synthetic HAC, only highly doped in sodium, were studied through a multidisciplinary approach by combining conventional and unconventional analytical techniques. Results highlighted that (i) sodium and silicon were mainly incorporated in a sodium-rich phase (Na-phase, NCA{sub 2}, Na{sub 1.9}CaAl{sub 3.9}Si{sub 0.1}O{sub 8}), (ii) no minor phases such as gehlenite and/or mayenite occurred, and (iii) CA (CaAl{sub 2}O{sub 4}) and CA{sub 2} (CaAl{sub 4}O{sub 7}) revealed a limited ionic substitution.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Microstructural and compositional evolutions in $γ$-LiAlO 2 pellets during ion irradiation at an elevated temperature

This study reports on the microstructural, phasic and compositional evolutions of γ-LiAlO 2 during ion irradiation. Polycrystalline γ-LiAlO 2 pellets were irradiated sequentially with He + and D 2 + ions to the same combined fluences of up to 3 × 10 17 (He + +D + )/cm 2 at 773 K. The irradiated pellets were characterized using scanning transmission electron microscopy and atom probe tomography. Surface amorphization likely due to radiolysis and planar defects as a possible precursor for formation of precipitates are created at 5 × 10 16 (He + +D + )/cm 2 , followed by the formation of nano-sized precipitates and fractures at higher doses. Spinel-like precipitates of non-stoichiometric LiAl 5 O 8 and gas-filled cavities are observed to grow with increasing dose. Faceted precipitates and rounded cavities appear at 2 × 10 17 (He + +D + )/cm 2 . With further increasing ion fluence to 3 × 10 17 (He + +D + )/cm 2 , amorphization of the precipitates takes place and micron-sized fractures appear. Surface exfoliation could occur at an extremely high ion fluence. There are compositional changes in the γ-LiAlO 2 pellets during the microstructural evolution. In the precipitate and amorphized regions, Li concentrations decrease to ~7 and 3.7 at.% from 25 at.% in γ-LiAlO 2 , respectively. This study reveals a full-cycle microstructural evolution with corresponding compositional changes in γ-LiAlO 2 pellets during ion irradiation at 773 K. In conclusion, the data could help model, assess, and predict the material performance during neutron irradiation in reactors.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Enhancement under UV–visible and visible light of the ZnO photocatalytic activity for the antibiotic removal from aqueous media using Ce-doped Lu3Al5O12 nanoparticles

We report the first synthesis of Ce-doped Lu{sub 3}Al{sub 5}O{sub 12} Nanoparticles/ZnO Nanostructure (LuAG:Ce/ZnO NS) via a rapid hydrolysis/condensation of Zn(OAc){sub 2} on the surface of LuAG:Ce NPs. The structural, morphological and optical properties of LuAG:Ce/ZnO NS have been fully investigated using X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), diffuse reflectance UV–visible spectroscopy and N2 adsorption/desorption measurements. Results showed that ZnO Nanocrystals (ZnO NCs) of about 10 nm diameter are homogeneously grown on the surface of 100 nm LuAG:Ce NPs in a core/shell-like structure. The photocatalytic activity of the as-prepared nanostructure has been evaluated throught the photodegradation of sulfathiazole (STZ), a molecule widely used as antibiotic, under UV–vis and visible light irradiation. Results showed that STZ undergoes much higher photodegradation in the presence of LuAG:Ce/ZnO NS compared to the pure ZnO NCs under both UV–vis and visible light. This enhanced photocatalytic capability was found to result from higher specific surface area and visible light absorption in LuAG:Ce/ZnO NS, which allowed for more surface active sites and enhanced hydroxyl radicals (·OH) production from the nanostructured photocatalyst. The recyclability of LuAG:Ce/ZnO NS was also demonstrated.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Microstructural evolution and precipitation in γ-LiAlO 2 during ion irradiation

Polycrystalline γ-LiAlO 2 pellets were sequentially irradiated with 120 keV He + and 80 keV D 2 + ions to the fluences of 1 × 10 17 and 2 × 10 17 (He + + D + )/cm 2 at 573 K. Additional irradiation was performed to a fluence of 2 × 10 17 (He + + D + )/cm 2 at 773 K. The irradiated pellets were characterized using scanning transmission electron microscopy, time-of-flight secondary ion mass spectrometry, and grazing incidence x-ray diffraction. Lattice damage, amorphization, and fractures are observed with no evidence for the formation of secondary-phase precipitates in the pellets irradiated up to an ion fluence of 2 × 10 17 (He + + D + )/cm 2 at 573 K. In contrast, faceted precipitates with sizes larger than 100 nm formed in a pellet irradiated to 2 × 10 17 (He + + D + )/cm 2 at 773 K. Analyses of the diffraction and composition data suggest that the precipitates have a spinel-type structure, likely a non-stoichiometric LiAl 5 O 8 with Li depletion. This could be an intermediate phase with Li atoms at the octahedral and possibly tetrahedral sites as well. It is speculated that as the dose increases, Li loss will continue and the precipitates will approach a composition of alumina primarily in phases of α-Al 2 O 3 and amorphized Al 2 O 3 .

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

Effect of the Reaction Medium on the Mechanochemical Synthesis of LiAlO{sub 2}

An unactivated mixture of aluminum hydroxide (gibbsite) and lithium carbonate and a mixture mechanically activated in an AGO-2 planetary mill were heat-treated in air and under vacuum (0.05 Pa) at temperatures of up to 800–850°C, and the phase composition of the heat treatment products was determined by in situ X-ray diffraction. The results demonstrate that, in the case of the unactivated mixture or after mechanical activation for 1 min, heat treatments in air and under vacuum lead to the formation of α-LiAlO{sub 2} and γ-LiAlO{sub 2}, respectively. After mechanical activation for 5 or 10 min, heat treatment both in air and under vacuum leads to γ-LiAlO{sub 2} formation. A possible mechanism behind the effect of the reaction medium on the phase composition of LiAlO{sub 2} is analyzed.

36 MATERIALS SCIENCE↗