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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Elucidating a dissolution–deposition reaction mechanism by multimodal synchrotron X-ray characterization in aqueous Zn/MnO 2 batteries

Aqueous Zn/MnO 2 batteries with their environmental sustainability and competitive cost, are becoming a promising, safe alternative for grid-scale electrochemical energy storage. Here, presented as a promising design principle to deliver a higher theoretical capacity, this work offers fundamental understanding of the dissolution–deposition mechanism of Zn/β-MnO 2 . A multimodal synchrotron characterization approach including three operando X-ray techniques (powder diffraction, absorption spectroscopy, and fluorescence microscopy) is coupled with elementally resolved synchrotron X-ray nano-tomography. Together they provide a direct correlation between structural evolution, reaction chemistry, and 3D morphological changes. Operando synchrotron X-ray diffraction and spectroscopy show a crystalline-to-amorphous phase transition. Quantitative modeling of the operando data by Rietveld refinement for X-ray diffraction and multivariate curve resolution (MCR) for X-ray absorption spectroscopy are used in a complementary fashion to track the structural and chemical transitions of both the long-range (crystalline phases) and short-range (including amorphous phases) ordering upon cycling. Scanning X-ray microscopy and full-field nano-tomography visualizes the morphology of electrodes at different electrochemical states with elemental sensitivity to spatially resolve the formation of the Zn- and Mn-containing phases. Overall, this work critically indicates that for Zn/MnO 2 aqueous batteries, the reaction pathways involving Zn–Mn complex formation upon cycling become independent of the polymorphs of the initial electrode and sheds light on the interplay among structural, chemical, and morphological evolution for electrochemically driven phase transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Towards a mechanistic understanding of the sol–gel syntheses of ternary carbides

Sol–gel chemistry, while being extremely established, is to this day not fully understood, and much of the underlying chemistry and mechanisms are yet to be unraveled. Here, in this work, we elaborate on the sol–gel chemistry of Cr 2 GaC, the first layered ternary carbide belonging to the MAX phase family to ever be synthesized using this wet chemical approach. Leveraging a variety of both in- and ex situ characterization techniques, including X-ray and neutron powder diffraction, X-ray absorption fine structure analyses, total scattering analyses, and differential scanning calorimetry coupled with mass spectrometry, in-depth analyses of the local structures and reaction pathways are elucidated. While the metals first form tetrahedrally and octahedrally coordinated oxidic structures, that subsequently grow and crystallize into oxides, the carbon source citric acid sits on a separate reaction pathway, that does not merge with the metals until the very end. In fact, after decomposing it remains nanostructured and disordered graphite until the temperature allows for the reduction of the metal oxides into the layered carbide. Based on this, we hypothesize that the method is mostly applicable to systems where the needed metals are reducible by graphite around the formation temperature of the target phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Pressure-induced tuning of the triangular-honeycomb structure of ferroelectric quantum spin liquid candidate, TbInO 3

The pressure response of the triangular-honeycomb-structured quantum spin liquid candidate, TbInO 3 , has been determined via neutron powder diffraction up to 5.75(5) GPa. The system retains hexagonal symmetry up to the maximum pressure considered. The structure was found to compress less anisotropically than related compounds, though it is more compressible within the 2D plane than between subsequent layers. Through extracting the O-atom coordinates we find experimental evidence that may suggest the enhancement of ferroelectricity at pressures as low as 3 GPa.

Ridley, Christopher J. [Oak Ridge National Laborat↗
DOE OSTI2025

Uptake and binding of La 3+ and Cr 3+ ions by alkali metal substituted alpha-zirconium phosphate

The conversion of alpha-zirconium phosphate, Zr(HPO 4 ) 2 ·H 2 O, to the K-, Rb-, and Cs-phases and the subsequent ion exchange behavior of these alkali metal phases, A-ZrP, with La 3+ and Cr 3+ have been investigated. The conversion to the A-ZrP phases was achieved by reaction with metal chloride, metal hydroxide solution, and confirmed through various techniques, including X-ray powder diffraction, thermogravimetry analysis, IR spectroscopy, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of material hydration, which increased the interlayer distance, was also examined. The ion exchange behavior of the A-ZrP showed strong affinity for both La 3+ , a representative for trivalent lanthanide metals, and Cr 3+ , a representative for the trivalent transition metals, with a rapid, near quantitative removal of the M 3+ ions at a pH of 3 when the ion concentration was ≤25% of the ion exchange capacity of the materials. Additionally, the ion affinity was shown to be pH and concentration-dependent, decreasing with a decrease in pH or an increase in ion concentration. Lastly, the binding strength of La- and Cr-loaded ZrP materials was examined through a series of leaching experiments in a carbonate buffer, phosphate buffer, HEPES buffer, and a series of EDTA solutions at various concentrations. No observable leaching occurred in the carbonate buffer, phosphate buffer, HEPES buffer, or when the EDTA concentration was below 0.1 mM. These results highlight the potential for the A-ZrP materials to provide a platform for trivalent transition metal and trivalent lanthanide radionuclide capture for various applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Mechanochemical α to β phase transition of U 3 O 8

Recognized as the most stable phase of uranium oxide, α-U 3 O 8 is widely used throughout the nuclear fuel cycle for safe storage and transportation. There is, however, a lack of understanding of the thermodynamic relationship between α-U 3 O 8 and its polymorph, β-U 3 O 8 . This research contributes new knowledge regarding the kinetics and mechanism of a previously described mechanochemical phase transition between the α- and β-U 3 O 8 polymorphs to improve the understanding of their thermodynamic relationship. In this work, tumble milling of α-U 3 O 8 using different milling media shows an ingrowth of the β-phase over time, with an observed correlation between media density, percent conversion and lattice strain. Anisotropic peak broadening observed within collected X-ray diffraction powder patterns suggests the preservation of uranium polyhedral layered sheets throughout the milling process. Preservation of the sheets implies a shear-induced slip mechanism occurring through in-plane shifting of uranium polyhedra along lattice planes perpendicular to the polyhedral sheets.

Roach, Jordan M. [Oak Ridge National Laboratory (O↗
DOE OSTI2025

Negative linear compressibility and complex phase behaviour in 7 Li 2 CO 3

We present a combination of neutron powder-diffraction measurements demonstrating negative linear compressibility and irregular thermal expansion in 7 Li 2 CO 3 . This is shown to be due to an interplay between the tilting of the rigid carbonate group and the shear strain in the unit cell, which leads to a first-order transition from monoclinic to hexagonal symmetry. The phase evolution is shown to be highly sensitive to the level of hydrostaticity in the sample. Under hydrostatic conditions, the sample begins transformation at 8.5 GPa leading to a change from tetrahedral to octahedral Li coordination. Symmetry adapted basis mode analysis, combined with density functional theoretical (DFT) calculations and Raman spectroscopy, is used to show that this transition is reverse proper ferroelastic in nature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Synthesis and characterization of zinc doped nano TiO{sub 2} for efficient photocatalytic degradation of Eriochrome Black T

Sol-gel method was used to synthesize undoped and zinc doped TiO{sub 2} with varied dopant concentrations using titanium tetraisopropoxide and zinc acetate as precursors. The synthesized catalyst samples were characterized by various techniques such as X-ray powder diffraction (XRD), UV-vis diffuse reflectance (DRS). The photocatalytic activity was determined by means of degradation of azo dye Eriochrome Black T. The results revealed that Zn doped TiO{sub 2} nanoparticles exhibited better results as compared to undoped TiO{sub 2} nanoparticles. Zn doped TiO{sub 2} (0.7mol %) nanoparticles exhibited the highest photocatalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Structural and spectroscopic analyses of europium doped yttrium oxyfluoride powders prepared by combustion synthesis

A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700 °C had a predominance of vernier orthorhombic Y{sub 6}O{sub 5}F{sub 8} phase, while samples heat treated at 800 °C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu{sup 3+}) in different concentrations (1–15 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu{sup 3+}:Y{sub 6}O{sub 5}F{sub 8} samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu{sup 3+}:YOF samples.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Effect of Pt promotion on Ni/Al{sub 2}O{sub 3} for the selective catalytic reduction of NO with hydrogen

Ni/Al{sub 2}O{sub 3} (10 wt.% Ni) and Ni-Pt/Al{sub 2}O{sub 3} (10 wt.% Ni, 0.5 wt.% Pt) were comparatively tested in the hydrogen selective catalytic reduction process (H{sub 2}-SCR), at reaction temperatures below 350°C. Catalytic activity tests consisted in temperature programmed reactions (TPRea) under plug flow conditions from 50 to 350°C, with a temperature rate of 5°C/min, using a feed stream with a reactant ratio NO:H{sub 2} = 1:1.3 and a GHSV of 4500 h{sup −1}. Promotion with Pt increases the catalytic performances of the Ni based catalyst, in respect to NO conversion, N{sub 2} selectivity and N{sub 2} yield. The reaction temperatures for NO conversion above 95% decrease significantly due to Pt addition, from 250°C for Ni/Al{sub 2}O{sub 3} to 125°C for Ni-Pt/Al{sub 2}O{sub 3}. Characterization of catalysts was performed by: X ray powder diffraction (XRD) for the estimation of Ni crystallite size, temperature programmed reduction (TPR) for the catalyst reducibility, temperature programmed desorption of hydrogen (H{sub 2}-TPD) for the investigation of active sites and metal dispersion on the support, N{sub 2} adsorption-desorption isotherms at −196°C for the determination of total specific surface area and pore size distribution, and H/D isotopic exchange on the catalyst surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Magnetic and elastic anisotropy in magnetorheological elastomers using nickel-based nanoparticles and nanochains

Nickel (Ni) based nanoparticles and nanochains were incorporated as fillers in polydimethylsiloxane (PDMS) elastomers and then these mixtures were thermally cured in the presence of a uniform magnetic field. In this way, macroscopically structured-anisotropic PDMS-Ni based magnetorheological composites were obtained with the formation of pseudo-chains-like structures (referred as needles) oriented in the direction of the applied magnetic field when curing. Nanoparticles were synthesized at room temperature, under air ambient atmosphere (open air, atmospheric pressure) and then calcined at 400 °C (in air atmosphere also). The size distribution was obtained by fitting Small Angle X-ray Scattering (SAXS) experiments with a polydisperse hard spheres model and a Schulz-Zimm distribution, obtaining a size distribution centered at (10.0 ± 0.6) nm with polydispersivity given by σ = (8.0 ± 0.2) nm. The SAXS, X-ray powder diffraction, and Transmission Electron Microscope (TEM) experiments are consistent with single crystal nanoparticles of spherical shape (average particle diameter obtained by TEM: (12 ± 1) nm). Nickel-based nanochains (average diameter: 360 nm; average length: 3 μm, obtained by Scanning Electron Microscopy; aspect ratio = length/diameter ∼ 10) were obtained at 85 °C and ambient atmosphere (open air, atmospheric pressure). The magnetic properties of Ni-based nanoparticles and nanochains at room temperature are compared and discussed in terms of surface and size effects. Both Ni-based nanoparticles and nanochains were used as fillers for obtaining the PDMS structured magnetorheological composites, observing the presence of oriented needles. Magnetization curves, ferromagnetic resonance (FMR) spectra, and strain-stress curves of low filler's loading composites (2% w/w of fillers) were determined as functions of the relative orientation with respect to the needles. The results indicate that even at low loadings it is possible to obtain magnetorheological composites with anisotropic properties, with larger anisotropy when using nanochains. For instance, the magnetic remanence, the FMR field, and the elastic response to compression are higher when measured parallel to the needles (about 30% with nanochains as fillers). Analogously, the elastic response is also anisotropic, with larger anisotropy when using nanochains as fillers. Therefore, all experiments performed confirm the high potential of nickel nanochains to induce anisotropic effects in magnetorheological materials.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Anomalous polarization in the antiferroelectric-ferroelectric phase coexistence state in PbZrO{sub 3}-Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}

The ferroelectric system (1−x)PbZrO{sub 3}-(x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3} has been investigated as a function of composition, temperature, and electric field by x-ray powder diffraction, dielectric, and ferroelectric measurements. Within the solubility limit (x ∼ 0.25), the system evolves from an orthorhombic-antiferroelectric to rhombohedral-ferroelectric state through a phase coexistence region. The highest polarization was found not for the composition exhibiting a pure ferroelectric state, but for a composition x = 0.15 exhibiting ferroelectric + antiferroelectric phase coexistence close to the rhombohedral phase boundary. Electric poling of the equilibrium two-phase state led to irreversible enhancement in the rhombohedral phase fraction suggesting that the enhanced polarization is related to the enhanced polarizability of the lattice due to first order criticality as in ferroelectric-ferroelectric morphotropic phase boundary systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Magnetic structure of the high temperature superconductor Gd{sub 1–x}Th{sub x}FeAsO

The magnetic structure of the high temperature superconductor Gd{sub 1–x}Th{sub x}FeAsO (x = 0, 0.25) has been determined by neutron powder diffraction. The Gd moments were found to order at T{sub N} ∼ 4 K and to lie in the basal plane, and form alternating ferromagnetic sheets along the c-axis. The orientation of the gadolinium moments in both the doped and undoped compounds has been confirmed using {sup 155}Gd Mössbauer spectroscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Magnetic phase transitions and entropy change in layered NdMn{sub 1.7}Cr{sub 0.3}Si{sub 2}

A giant magnetocaloric effect has been observed around the Curie temperature, T{sub C} ∼ 42 K, in NdMn{sub 1.7}Cr{sub 0.3}Si{sub 2} with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320 K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10–400 K) confirmed the magnetic transitions and phases as follows: T{sub N}{sup intra} ∼ 380 K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), T{sub N}{sup inter} ∼ 320 K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while T{sub C} ∼ 42 K denotes the first order magnetic transition from AFmc to canted ferromagnetism (Fmc + F(Nd)) due to ordering of the Mn and Nd sub-lattices. The maximum values of the magnetic entropy change and the adiabatic temperature change, around T{sub C} for a field change of 5 T are evaluated to be −ΔS{sub M}{sup max} ∼ 15.9 J kg{sup −1} K{sup −1} and ΔT{sub ad}{sup max} ∼ 5 K, respectively. The first order magnetic transition associated with the low levels of hysteresis losses (thermal <∼0.8 K; magnetic field <∼0.1 T) in NdMn{sub 1.7}Cr{sub 0.3}Si{sub 2} offers potential as a candidate for magnetic refrigerator applications in the temperature region below 45 K.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Novel ferroelectric single crystals of Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} ternary solid solution

Ferroelectric single crystals of a new lead-reduced Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} (BZT-PZ-PT) ternary solid solution system have been grown for the first time by three different methods, namely high temperature solution growth (HTSG, or flux method), top-cooled solution growth (TCSG), and top-seeded solution growth (TSSG). The chemical and thermodynamic parameters, including the flux concentration, the soaking temperature and the cooling rate, have been optimized, leading to the growth of good quality BZT-PZ-PT crystals of pseudo-cubic morphology. A large size crystal of the dimensions of 2 × 2 × 0.5 cm{sup 3} has been obtained by the TSSG technique. The crystal structure is analyzed by means of X-ray powder diffraction. The highest ferroelectric Curie temperature T{sub C} of the grown crystals is found to be 320 °C by means of dielectric measurements. A remnant polarization of 32 μC/cm{sup 2} is displayed with a coercive field of 15.4 kV/cm. The high T{sub C} and large coercive field of the BZT-PZ-PT single crystal make this material a promising candidate for applications in high power electromechanical transducers that can operate in a wider temperature range and at high fields.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Textured PrCo{sub 5} nanoflakes with large coercivity prepared by low power surfactant-assisted ball milling

The effect of the milling time on the structure, morphology, coercivity, and remanence ratio of textured PrCo{sub 5} nanoflakes produced by low power surfactant-assisted ball milling (SABM) was investigated. The X-ray powder diffraction (XRD) patterns indicate that the SABM PrCo{sub 5} samples are all CaCu{sub 5}-type hexagonal structure. The average grain size is smaller than 10 nm when the SABM time is equal to or longer than 5.5 h. The thickness of nanoflakes is mainly in the range of 50−100 nm while the length is 0.5−5 μm when the SABM time reaches 8 h. For the field-aligned PrCo{sub 5} nanoflakes, the out-of-plane texture is indicated from the increasing (0 0 l) peaks in the XRD patterns, and the easy magnetization direction is perpendicular to the flake surface. The strong texture of PrCo{sub 5} nanoflakes leads to a large coercivity H{sub c} (7.8 kOe) and obvious anisotropic magnetic behaviors for the aligned samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Thermoelectric study of crossroads material MnTe via sulfur doping

Here, we report thermoelectric study of crossroads material MnTe via iso-electronic doping S on the Te-site. MnTe{sub 1-x}S{sub x} samples with nominal S content of x = 0.00, 0.05, and 0.10 were prepared using a melt-quench method followed by pulverization and spark plasma sintering. The X-ray powder diffraction, scanning electron microscopy, and ZAF-corrected compositional analysis confirmed that S uniformly substitutes Te up to slightly over 2%. A higher content of S in the starting materials led to the formation of secondary phases. The thermoelectric properties of MnTe{sub 1-x}S{sub x} samples were characterized by means of Seebeck coefficient, electrical conductivity, and thermal conductivity measurements from 300 K to 773 K. Furthermore, Hall coefficient measurements and a single parabolic band model were used to help gain insights on the effects of S-doping on the scattering mechanism and the carrier effective mass. As expected, S doping not only introduced hole charge carriers but also created short-range defects that effectively scatter heat-carrying phonons at elevated temperatures. On the other hand, we found that S doping degraded the effective mass. As a result, the ZT of MnTe{sub 0.9}S{sub 0.1} was substantially enhanced over the pristine sample near 400 K, while the improvement of ZT became marginal at elevated temperatures. A ZT ∼ 0.65 at 773 K was obtained in all three samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

New metal-organic nanomaterials synthesized by laser irradiation of organic liquids

A new type of metal-organic composition consisting of clusters of nanoparticles has been synthesised by laser irradiation of metallocene/benzene solutions. The metallocene molecules in this reaction become the source of the metal. Exposure to high-energy femtosecond laser pulses dehydrogenate benzene molecules and initiate the high-temperature high-pressure conditions that results in the synthesis of new materials. Irradiation experiments have been carried out on ferrocene/benzene and on other solutions. With ferrocene the synthesis of a new compound has been confirmed by X-ray powder diffraction as the peaks detected do not correspond to any known substance in the Crystallography Open Database. Theoretical simulation of the periodic structure of this new carbide predicts that it has hexagonal symmetry and a unit cell with a = 3.2A and c =2.8A. The exact structure is still uncertain but may be determined from scanning tunneling microscope (STM) studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4}

[N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} hybrid compound is crystallized at room temperature (T ≈ 300 K) in the orthorhombic system with Pnma space group. Five phase transitions (T{sub 1} = 255 K, T{sub 2} = 282 K, T{sub 3} = 302 K, T{sub 4} = 320 K, and T{sub 5} = 346 K) have been proved by DSC measurements. The electrical technique was measured in the 10{sup −1}-10{sup 7} Hz frequency range and 233–363 K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗