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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Decontamination of Radio-Cs in Soil and Incineration Fly Ash to the Clearance Level by Pyrolysis - 18247

Radio-Cs generated by the Fukushima Daiichi Nuclear Power Plant accident is decontaminated from contaminated soil and incineration fly ash to the clearance level via pyrolysis treatment. By adjusting the chemical composition of soil and ash to be in line with ordinary Portland cement, OPC and adding a small amount of CaCl{sub 2}, radio- and stable Cs can evaporate almost completely and be collected by a bag filter system after cooling in the form of chlorides as a component of potassium chloride. Laboratory-scale experiments have produced cement with a radio-Cs content of less than the detection limit from several grams of pond sediments having an initial radio-Cs content of 9293 Bq/kg via burning at over 1275 deg. C using a small-scale rotating furnace. It is also possible to decontaminate radio-Cs from incineration fly ash using the same system. OPC complying with the clearance level for radio-Cs is produced as a product of this system and the basic components are confirmed via X-ray diffraction and Rietveld analysis. In order to obtain a suitable cement mineral composition, a burning temperature of 1400 or 1450 deg. C is required. Using a pilot-scale kiln, 100 kg of OPC is produced from imitated soil with the addition of Cs{sub 2}CO{sub 3}, calcined, and then burned at 1450 deg. C. The produced cement cleared the required basic performances specified by Japanese industrial standards. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Size-dependent structural phase transitions and their correlation with photoluminescence and optical absorption behavior of annealed Zn0.45Cd0.55S quantum dots

Highlights: • Thermal Induced Structural Phase transition in nanostructured Zn{sub 0.45}Cd{sub 0.55}S. • Low temperature structural phase transition from cubic to hexagonal structure. • Thermal annealing effect on FTIR and Raman Spectra. • Thermal annealing effect on optical absorption of Zn{sub 0.45}Cd{sub 0.55}S nanoparticles. • Excitation-wavelength dependent photoluminescence emission spectra. - Abstract: In this paper, we investigate the effect of thermally induced structural phase transitions on the photoluminescence (PL) and optical absorption behaviour of Zn{sub 0.45}Cd{sub 0.55}S nanoparticles (NPs). Analysis of X-ray diffraction (XRD) patterns and high-resolution electron microscope (HRTEM) images reveal that the as-synthesized sample possesses zinc-blende-type cubic structure. In addition, at annealing temperature (T{sub a}) 400 °C, the cubic structure transforms completely into the wurtzite-type hexagonal structure. Furthermore, the second phase transition of the as-synthesized sample has observed at 700 °C, where the cubic structure has transformed into mixed polycrystalline phases of hexagonal ZnO, cubic CdO, monoclinic CdSO{sub 3}, and orthorhombic ZnSO{sub 4} structures. These new phases have also confirmed from the analysis of Raman and FTIR spectra. Analysis of UV–visible optical absorption spectra demonstrates that Increasing T{sub a} results in the decrease of optical band gap due the improvement in crystallinity accompanied by the increase in the particle size. The PL emission bands at an excitation energy of 3.818 eV exhibit redshift and a decrease in the intensity with increasing T{sub a} up to 500 °C. Meanwhile, further increase in T{sub a} up to 700 °C results in the enhancement of green emission intensity. On the other hand, PL emission spectra at 3.354 eV and T{sub a} 700 °C, reveal a dramatic increase in the emission intensity nearly by one-order of magnitude with respect to its value of the as-synthesized sample. This behaviour is ascribed to the incorporation of oxygen-related defects via thermal annealing in air, which act as additive radiative centers. Also, we have interpreted the observed spectral blue shift of PL emission spectrum with increasing excitation energy.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

New Diphosphopentamolybdate K{sub 5}[HP{sub 2}Mo{sub 5}O{sub 23}] · 10H{sub 2}O: Synthesis, Structure, and Characterization

A new diphosphopentamolybdate(VI) K{sub 5}[HP{sub 2}Mo{sub 5}O{sub 23}] · 10H{sub 2}O has been prepared employing solution method and characterized by single crystal X-ray diffraction, energy dispersive analysis, infrared spectroscopy, thermal stability analysis, cyclic voltammetry analysis, and ultraviolet visible spectroscopy. The compound crystallizes in the orthorhombic sp. gr. Pcab: a = 15.9661(10) Å, b = 19.0832(10) Å, c = 20.0970(9) Å, V = 6123.27(10) Å3, Z = 8. The crystal structure contains the polyanion units [HP{sub 2}Mo{sub 5}O{sub 23}]{sup 5–} around the potassium cations and lattice water. The [HP{sub 2}Mo{sub 5}O{sub 23}]{sup 5–} subunits are connected together through K−O−Mo bridges and hydrogen bonds. The crystal shape morphology was simulated using the Bravais–Friedel–Donnay–Harker model.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Assessment of lead tellurite glass for immobilizing electrochemical salt wastes from used nuclear fuel reprocessing

This paper provides an overview of research evaluating the use of lead tellurite glass as a waste form for salt wastes from electrochemical reprocessing of used nuclear fuel. The efficacy of using lead tellurite glass to immobilize three different salt compositions was evaluated: a LiCl-Li2O oxide reduction salt containing fission products from oxide fuel, a LiCl-KCl eutectic salt containing fission products from metallic fuel, and SrCl2. Physical and chemical properties of glasses made with these salts were characterized with X-ray diffraction, bulk density measurements, differential thermal analysis, chemical durability tests, scanning and transmission electron microscopies, and energy-dispersive X-ray spectroscopy. These glasses were found to accommodate high salt concentrations and have high densities, but further development is needed to improve chemical durability. (C) 2017 Published by Elsevier B.V.

Riley, Brian J.↗
DOE OSTI2017

Synthesis, Structure, and Fluorescence of a Novel Cadmium Compound

A novel cadmium compound, [(CdI{sub 3}){sub 2}(μ{sub 2}-I)]{sub 2}(Me{sub 2}-4,4'-H{sub 2}bipy){sub 3} (1) (Me = methyl; 4,4'-bipy = 4,4'-bipyridine) with the Me{sub 2}-4,4'-H{sub 2}bipy moiety generated in situ, has been prepared through a solvothermal reaction and structurally characterized by X-ray single crystal diffraction analysis. Compound 1 is characterized by an isolated structural motif, consisting of [(CdI{sub 3}){sub 2}(μ{sub 2}-I)]{sup 3–} anions and Me{sub 2}-4,4'-H{sub 2}bipy{sup 2+} cations. The [(CdI{sub 3}){sub 2}(μ{sub 2}-I)]{sup 3–} anions and Me{sub 2}-4,4'-H{sub 2}bipy{sup 2+} cations interconnect together via C–H···I hydrogen-bonding interactions to complete a three-dimensional (3D) supramolecular network. Solid state fluorescent spectrum reveals an emission band in the violet region.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Synthesis and photoluminescence properties of LiSrPO{sub 4}:Eu{sup 2+} phosphor for solid state lighting

A novel method to prepare orthophosphate LiSrPO{sub 4}: Eu{sup 2+} phosphor for white light-emitting diodes (w-LEDs) is given in this paper. Phosphor was successfully synthesized by Pechini (citrate gel) method which is efficient than conventional high temperature solid state reaction. X-ray powder diffraction (XRD) analysis confirmed the single phase formation of LiSrPO{sub 4}:Eu{sup 2+} with monoclinic crystal structure. Luminescence results showed that the phosphor could be efficiently excited by near UV and exhibited bright blue emission at λ{sub em} = 420 nm corresponding to 5d– 4f transition of Eu{sup 2+}. The phosphor exhibits blue emission bands under 350 nm excitation. This mercury-free excitation is useful for solid state lighting and light-emitting diode (LED). Hence it could be useful for solid state lighting and light-emitting diode (LED) application.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Studies on the Encapsulation of Brine Generated from a Process Using Selective Electrodialysis Reversal

This topical report summarizes the laboratory testing, geochemical modeling, and mineralogical testing conducted to examine the efficacy of wastewater encapsulation for the brine generated from the Saltworks Flex electrodialysis reversal technology. Within the laboratory testing, the short- and long-term physical properties of seven separate mix designs were examined along with the leaching of each mix design. Additionally, geochemical thermodynamic modeling was used along with mineralogical analyses to help gain a fundamental understanding of the chemistry involved in the encapsulation process. Encapsulation is a process that results in the immobilization of constituents of interest by creating an engineered material that contains the waste within its matrix, both physically and chemically, in such a manner that the receiving environment is protected from adverse effects. Within the context of this study, encapsulation mix designs involved mixing the Saltworks brine with fly ash and various additives, principally lime (calcium oxide) and cement, to form a paste that eventually sets and hardens into a monolith upon placement in a landfill. Moisture conditioning fly ash with wastewater sources for on-site landfill disposal is a process that is in use at some sites and has been presented as a viable option to dispose of liquid wastes. However, because chemical reactions that can lead to sequestration of constituents of interest are not optimized, leaching can occur. Therefore, in this study, mixes were created to mimic moisture conditioning, as well as engineered pastes of varying mix designs. The study found that engineered encapsulation mixes provide significant resistance to leaching compared to moisture conditioning alone. The best performing encapsulation mix used lime as the additive, which proved superior to the use of cement. After 90 days of curing, this encapsulated mix was 5.5 times stronger than the moisture conditioned mix. Additionally, this mix exhibited an approximate 2.5 order of magnitude drop in hydraulic conductivity compared to the moisture conditioned mix. When comparing leaching, nearly all the chloride was found to evolve from the moisture conditioned mix, whereas only 6.7% of the chlorine contained in the best performing encapsulated mix leached out. Mineralogical analysis via X-ray diffraction (XRD) showed a significant concentration of the chloride sequestering mineral, Friedel’s salt, in the best performing encapsulation mix, whereas none was observed in the moisture conditioned mix, pointing to it being the primary chemical mechanism for chloride retention, along with the physical impermeability of the material. With respect to the modeling study, the model was successful in predicting the presence of most mineral phases observed in the XRD analysis.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2019

Magnetic Properties of Ru-Doped Nd{sub 0.67}Sr{sub 0.33}Mn{sub 1−x}Ru{sub x}O{sub 3} (0 ≤ x ≤ 0.10) Manganites

The structural and magnetic properties of polycrystalline Nd{sub 0.67}Sr{sub 0.33}Mn{sub 1−x}Ru{sub x}O{sub 3} (x = 0.00 and 0.10) samples have been studied with the substitution of Ru at Mn site. The samples have orthorhombic crystal structure determined by room-temperature X-ray diffraction and Rietvield analysis. On Ru doping at Mn site, a change in its symmetry space group is observed. The increase in Ru content significantly affects the Curie temperature (T{sub c}). The double-exchange mechanism is suppressed with Ru doping affecting the Mn{sup 3+}–O{sup 2−}–Mn{sup 4+} ion network. Paramagnetic regime of samples in magnetization-temperature graph is fitted and analyzed with Curie-Weiss law. The magnetization versus applied magnetic field measurements show that the samples exhibit ferromagnetic behavior at lower temperatures and paramagnetic behavior at room temperature with negligible hysteresis loop and low coercive field.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Chemical state mapping of simulant Chernobyl lava-like fuel containing material using micro-focused synchrotron X-ray spectroscopy

Uranium speciation and redox behaviour is of critical importance in the nuclear fuel cycle. X-ray absorption near-edge spectroscopy (XANES) is commonly used to probe the oxidation state and speciation of uranium, and other elements, at the macroscopic and microscopic scale, within nuclear materials. Two-dimensional (2D) speciation maps, derived from microfocus X-ray fluorescence and XANES data, provide essential information on the spatial variation and gradients of the oxidation state of redox active elements such as uranium. In the present work, we elaborate and evaluate approaches to the construction of 2D speciation maps, in an effort to maximize sensitivity to the U oxidation state at the U L 3 -edge, applied to a suite of synthetic Chernobyl lava specimens. Our analysis shows that calibration of speciation maps can be improved by determination of the normalized X-ray absorption at excitation energies selected to maximize oxidation state contrast. The maps are calibrated to the normalized absorption of U L 3 XANES spectra of relevant reference compounds, modelled using a combination of arctangent and pseudo-Voigt functions (to represent the photoelectric absorption and multiple-scattering contributions). We validate this approach by microfocus X-ray diffraction and XANES analysis of points of interest, which afford average U oxidation states in excellent agreement with those estimated from the chemical state maps. This simple and easy-to-implement approach is general and transferrable, and will assist in the future analysis of real lava-like fuel-containing materials to understand their environmental degradation, which is a source of radioactive dust production within the Chernobyl shelter.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Effect of (Sr{sub 0.7}Ca{sub 0.3})TiO{sub 3}-substitution on structure, dielectric, ferroelectric, and magnetic properties of BiFeO{sub 3} ceramics

Bi{sub 1−x}(Sr{sub 0.7}Ca{sub 0.3}){sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} ceramics were prepared by a standard solid state reaction process, and the influence of Sr/Ca ratio on structure and properties for Bi{sub 1−x}(Sr,Ca){sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} system was discussed by comparing with Sr{sub 0.5}Ca{sub 0.5}TiO{sub 3}-modified BiFeO{sub 3} ceramics. Rietveld analysis of X-ray diffraction data revealed that the crystal structure changed from rhombohedral R3c (x ≤ 0.4) to orthorhombic Pnma (x = 0.6) with Sr{sub 0.7}Ca{sub 0.3}TiO{sub 3} substitution, and biphasic structure (R3c + Pnma) was determined at x = 0.5, while that for Bi{sub 1−x}(Sr{sub 0.5}Ca{sub 0.5}){sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} system was at x = 0.4. This indicated that the morphotropic phase boundary in Bi{sub 1−x}(Sr,Ca){sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} system shifted toward (Sr,Ca)TiO{sub 3} side with increasing Sr/Ca ratio. The Raman spectrometric analysis and selected area electron diffraction analysis also confirmed this transition. The dielectric relaxation could be well fitted by Arrhenius law, and the different activation energies were attributed to the different origins of the dielectric relaxations with increasing temperature. The current density-field (J-E) curves indicated that the leakage current was reduced to about five orders of magnitude with Sr{sub 0.7}Ca{sub 0.3}TiO{sub 3} substitution. The P-E hysteresis loops obtained by three different methods indicated the enhanced ferroelectricity at x = 0.4, and it could be attributed to the decrement of leakage current. Meanwhile, the magnetization was enhanced with Sr{sub 0.7}Ca{sub 0.3}TiO{sub 3} substitution, and the maximum remanent magnetization was determined at x = 0.2. The enhanced magnetization originated from the partial substitution of Fe{sup 3+} by Ti{sup 4+}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Martensitic transformation behavior in Ti–Ni–X (Ag, In, Sn, Sb, Te, Tl, Pb, Bi) ternary alloys

Graphical abstract: - Highlights: • Ag, In and Sn were soluble in TiNi matrix, while Sb, Te, Tl, Pb and Bi were not. • The B2-R-B19′transformation occurred in Ti-Ni-(Ag, In, Sn) alloys. • Solid solution hardening was essential for inducing the B2-R transformation. - Abstract: The microstructures and transformation behaviors of Ti–Ni–X (Ag, In, Sn, Sb, Te, Tl, Pb, Bi) ternary alloys were investigated using electron probe micro-analysis (EPMA), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Micro Vickers hardness tests. All specimens consisted of Ti–Ni matrices and second phase particles. Ag, In and Sn were soluble in Ti–Ni matrices with a limited solubility (≤1.0 at%), while Sb, Te, Tl, Pb and Bi were not soluble. Two-stage B2-R-B19′ transformation occurred in Ti–48.8Ni–1.2Ag, Ti–49.0Ni–1.0In and Ti–49.0Ni–1.0Sn alloys, while one-stage B2-B19′ transformation occurred in Ti–49.0Ni–1.0Ag, Ti–49.0Ni–1.0Sb, Ti–49.0Ni–1.0Te, Ti–49.0Ni–1.0Pb and Ti–49.0Ni–1.0Bi alloys. Micro Vickers hardness of the alloys displaying the B2-R-B19′ transformation (Hv 250–368) was much larger than that (<Hv 200) of the alloys displaying the B2-B19′ transformation. Solid solution hardening was an important factor for inducing the B2-R transformation in Ti–Ni–X (X = non-transition elements) alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nonlinear Resonance Response of Porous Beam-Type Implants Corresponding to Various Morphology Shapes for Bone Tissue Engineering Applications

Having excellent biocompatibility and apatite mineralization as well as efficient mechanical properties makes bredigite as one of the most attractive bioceramics. A beam-type porous biological implant in a 3D-printed architecture is designed with micron pore size. The surface properties, morphology, and size of the composed powders are evaluated using Scherrer and Williamson-Hall equation. The effect of MNPs deposition into the bredigite bioceramics and correlation with temperature effect on roughness of the prepared bio-nanocomposite are also investigated for hyperthermia application potential. The composed powders are characterized by x-ray diffraction, and then scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (weight change, TGA), and atomic force microscopy are utilized to evaluate the surface topography. The resonance response is the tendency of a bone scaffold to respond at prominent amplitude while the frequency of its oscillations is equal to the structure’s natural frequency of vibration. Therefore, based on the obtained mechanical properties via the experimental approach for the bio-nanocomposite material, an analytical solution based upon the multiple-timescale method is carried out to analyze the nonlinear primary resonance of a 3D-printed porous beam-type biological implant under uniform-distributed load. According to SEM observations, there are hard agglomerates in the bredigite-magnetite nanoparticles (Br-MNPs) bio-nanocomposite material with low weight fraction of MNPs. However, they are broken down by increasing the amount of MNPs. Also, it is displayed that for lower MNPs weight fraction, the height of jump phenomenon related to the nonlinear resonance response is maximum and minimum for, respectively, irregular and mesoporous shapes of morphology, but their associated forcing amplitudes related to the bifurcation points are minimum and maximum, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Electric-field-induced strain contributions in morphotropic phase boundary composition of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-BaTiO{sub 3} during poling

The microscopic contributions to the electric-field-induced macroscopic strain in a morphotropic 0.93(Bi{sub 1/2}Na{sub 1/2}TiO{sub 3})−0.07(BaTiO{sub 3}) with a mixed rhombohedral and tetragonal structure have been quantified using full pattern Rietveld refinement of in situ high-energy x-ray diffraction data. The analysis methodology allows a quantification of all strain mechanisms for each phase in a morphotropic composition and is applicable to use in a wide variety of piezoelectric compositions. It is shown that during the poling of this material 24%, 44%, and 32% of the total macroscopic strain is generated from lattice strain, domain switching, and phase transformation strains, respectively. The results also suggest that the tetragonal phase contributes the most to extrinsic domain switching strain, whereas the lattice strain primarily stems from the rhombohedral phase. The analysis also suggests that almost 32% of the total strain is lost or is a one-time effect due to the irreversible nature of the electric-field-induced phase transformation in the current composition. This information is relevant to on-going compositional development strategies to harness the electric-field-induced phase transformation strain of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-based lead-free piezoelectric materials for actuator applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Analysis of Mullite Formation in the Core Glass of a Chromium-Doped Aluminosilicate Fiber

Using MCVD, we have produced optically active fibers with a glass-ceramic core containing mullite, 3Al{sub 2}O{sub 3} · 2SiO{sub 2}, as a major crystalline phase. Thermodynamic prediction of mullite formation conditions has been supplemented by thermal analysis and X-ray diffraction characterization of preform core samples, and fiber heat treatment (annealing) conditions have been established. Luminescence measurements for the fibers annealed under optimal conditions demonstrate that optically active chromium has a crystalline local environment.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Synthesis and photoluminescence properties of ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) red phosphor

Highlights: • The ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) red phosphors were synthesized. • Photoluminescence (PL) properties of ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) phosphors also were discussed. • ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) could be a potential red phosphor for NUV LEDs and displays. - Abstract: ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) oxyapatite phosphors have been synthesized via traditional solid-state methods X-ray powder diffraction (XRD) analysis confirmed the phase formation of ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) materials. The scanning electron microscope (SEM) image exhibited the irregular morphology of ALa{sub 9}(SiO{sub 4}){sub 6}O{sub 2}: Eu{sup 3+} (A = Li, Na) particles. The photoluminescence excitation (PLE) and emission (PL) spectra were investigated. The results showed that the phosphor could be efficiently excited by the near ultraviolet (NUV) light, and it exhibited red light emission. The calculated color coordinates lies in the red region. All the obtained results suggest that the prepared phosphors exhibit great potential application as red emitting phosphor for near ultraviolet white light emitting diodes (NUV WLEDs).

36 MATERIALS SCIENCE↗
DOE OSTI2016

Nanostructure formation during accumulative roll bonding of commercial purity titanium

In this investigation, commercial purity titanium (CP–Ti) was subjected to accumulative roll bonding (ARB) process up to 8 cycles (equivalent strain of 6.4) at the ambient temperature. Transmission electron microscopy (TEM) and X–ray diffraction line profile analysis (XRDLPA) were utilized to investigate the microstructure and grain size evolution. Both characterization techniques could clarify the non–uniform microstructure in the early stages and the uniform microstructure in the final stages of the process. The effectiveness of ARB for the fabrication of the nano–grained structure in CP–Ti was revealed. It was found that the SFE is not the only factor affecting grain refinement, as compared with other studies on ARB of FCC materials. Influence of other factors such as the melting temperature and the crystalline structure of the material was determined on the grain refinement. - Highlights: •Nano–grained commercial purity titanium was produced by accumulative roll bonding. •TEM and XRDLPA were used for the characterization of the microstructure. •Important factors affecting the grain size of ARBed materials were discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A novel orange-red emitting NaCaVO{sub 4}:Sm{sup 3+} phosphor for solid state lighting

The samarium doped NaCaVO{sub 4} phosphor was synthesized by the combustion method. The X-ray powder diffraction (XRD) analysis confirmed that the phosphor powder crystallized as orthorhombic structure belonging to space group Cmcm. From Williamson-Hall analysis the grain size and microstrain in the powder was estimated. The Fourier- transform infrared (FT-IR) studies further validated the formation of vanadate phase of the phosphor. Photoluminescence (PL) study revealed that the phosphor could be efficiently excited by UV-VIS from 200 nm to 500 nm. The 565 nm, 602 nm, 648 nm and 713 nm emissions were ascribed to {sup 4}G{sub 5/2} to {sup 6}H{sub J} (J = 5/2, 7/2, 9/2 and 11/2) transitions of the Sm{sup 3+} ion. The present material may be explored as a novel phosphor to be excited by UV light emitting diodes (LEDs) chips for solid-state lighting and display applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Effects of Co doping on the structure and physicochemical properties of hausmannite (Mn 3 O 4 ) and its transformation during aging

Hausmannite is a common low-valence manganese oxide mineral with a distorted spinel structure in surficial sediments. Although natural Mn oxides often contain various transition metal (TM) impurities, few studies have addressed the substitution mechanisms of TMs, such as cobalt (Co), with hausmannite and induced changes in the mineral physicochemical properties. In this study, Co-doped hausmannites with final Co/Mn molar ratios of 0.05 and 0.11 were synthesized and characterized by wet chemical analysis, powder X-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS). Co-doped samples have larger crystallite sizes and smaller specific surface areas than those of the hausmannite without Co. The Co cations exist in a mixed-valence of +3 and + 2. Powder XRD and acid dissolution experiments indicate that Co incorporates into the mineral structures, and increases the mineral structural stability. Co K-edge extended X-ray adsorption fine structure (EXAFS) analysis demonstrates that Co likely substitutes for lattice Mn(III). After aging at room temperature for three years, 14.1 ± 1.9% of pure hausmannite is transformed to manganite while only 2.6 ± 0.7% of manganite appears in the aged Co-doped sample with an initial Co/Mn molar ratio of 0.10. Finally, these results provide new insights into the incorporation mechanisms of TMs into low valence Mn oxides, and the stability of these minerals in natural environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗