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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Novel ethylenediamine-gallium phosphate containing 6-fold coordinated gallium atoms with unusual four equatorial Ga–N bonds

A novel ethylenediamine-gallium phosphate, formulated as Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, was synthesized under hydrothermal conditions. The crystal structure, including hydrogen positions, was determined using single-crystal X-ray diffraction data (monoclinic, a=9.4886(3) Å, b=6.0374(2) Å, c=10.2874(3) Å, and β=104.226(3)°, space group Pc) and the bulk was characterized by chemical (Ga–P–C–H–N) and thermal analysis (TG–MS and DSC), including activation energy data of its thermo-oxidative degradation, powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (SS-NMR) measurements, and transmission electron microscopy (TEM, SAED/NBD, and STEM BF-EDX). The crystal structure is built up of infinite zig-zag chains running along the c-axis, formed by vertex-shared (PO{sub 4}) and (GaO{sub 2}N{sub 4}) polyhedra. The new compound is characterized by unusual four equatorial Ga–N bonds coming from two nonequivalent ethylenediamine molecules and exhibits strong blue emission at 430 nm (λ{sub ex}=350 nm) in the solid state at room temperature. - Graphical abstract: Single crystals of a new ethylenediamine-gallium phosphate, Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, were obtained and the structural features presented. This structure is one of the scarce examples of GaPO with Ga–N bonds reported. - Highlights: • A novel ethylenediamine-gallium phosphate was hydrothermally synthesized. • The new compound is characterized by unusual four equatorial Ga–N bonds. • Void-volume analysis shows cages and channels with sizes ideally suited to accommodate small molecules. • The new compound exhibits strong blue emission.

36 MATERIALS SCIENCE↗
NASA NTRS1975

Analytical displacements and vibrations of cantilevered unsymmetric fiber composite laminates

A fiber composite flat cantilever plate that has symmetric and nonsymmetric laminate configurations is theoretically investigated to determine its static and dynamic structural response. The finite element analysis method used includes a unique triangular finite element developed at Lewis for the analysis of fiber composite airfoils. The various responses investigated include tip displacements, natural frequencies, and fundamental mode shapes. The results show that laminate configurations may be selected for a cantilever such that when the tip at the leading edge is loaded normal to the plane of the plate, the tip at the trailing edge can (1) deflect in the opposite direction, (2) deflect about the same, or (3) deflect more than the tip at the leading edge. This variation in response can be utilized to provide built-in structural damping to resist flutter.

Minich, M. D.↗
NASA NTRSDate not supplied

Variational Coupled Loads Analysis using the Hybrid Parametric Variation Method

Time-domain coupled loads analysis (CLA)is used to determine the response of a launch vehicle and payload system to transient forces, such as liftoff, engine ignitions and shutdowns, jettison events, and atmospheric flight loads, such as buffet. CLA, using Hurty/Craig-Bampton (HCB)component models, is the accepted method for the establishment of design-level loads for launch systems. However, uncertainty in the component models flows into uncertainty in predicted system results. Uncertainty in the structural responses during launch is a significant concern because small variations in launch vehicle and payload mode shapes and their interactions can result in significant variations in system loads. Uncertainty quantification (UQ)is used to determine statistical bounds on prediction accuracy based on model uncertainty. In this paper uncertainty is treated at the HCB component-model level. In an effort to account for model uncertainties and statistically bound their effect on CLA predictions, this work combines CLA with UQ in a process termed variational coupled loads analysis (VCLA). The modeling of uncertainty using a parametric approach, in which input parameters are represented by random variables, is common, but its major drawback is the resulting uncertainty is limited to the form of the nominal model. Uncertainty in model form is one of the biggest contributors to uncertainty in complex built-up structures. Model-form uncertainty can be represented using a nonparametric approach based on random matrix theory (RMT). In this work, UQ is performed using the hybrid parametric variation (HPV)method, which combines parametric with nonparametric uncertainty at the HCB component model level. The HPV method requires the selection of dispersion values for the HCB fixed-interface (FI)eigenvalues, and the HCB mass and stiffness matrices. The dispersions are based upon component test-analysis modal correlation results. During VCLA, random component models are assembled into an ensemble of random systems using a Monte Carlo (MC)approach. CLA is applied to each of the ensemble members to produce an ensemble of system-level responses for statistical analysis. The proposed methodology is demonstrated through its application to a buffet loads analysis of NASA’s Space Launch System (SLS)during the transonic regime fifty seconds after liftoff. Core stage (CS)section shears and moments are recovered, and statistics are computed.

Uncertainty Quantification↗
DOE OSTI2016

Centrosymmetry vs noncentrosymmetry in La{sub 2}Ga{sub 0.33}SbS{sub 5} and Ce{sub 4}GaSbS{sub 9} based on the interesting size effects of lanthanides: Syntheses, crystal structures, and optical properties

Two new quaternary sulfides La{sub 2}Ga{sub 0.33}SbS{sub 5} and Ce{sub 4}GaSbS{sub 9} have been prepared from stoichiometric elements at 1223 K in an evacuated silica tube. Interestingly, La{sub 2}Ga{sub 0.33}SbS{sub 5} crystallizes in the centrosymmetric structure, while Ce{sub 4}GaSbS{sub 9} crystallizes in the noncentrosymmetric structure, which show obvious size effects of lanthanides on the crystal structures of these two compounds. Ce{sub 4}GaSbS{sub 9} belongs to RE{sub 4}GaSbS{sub 9} (RE=Pr, Nd, Sm, Gd–Ho) structure type with a=13.8834(9) Å, b=14.3004(11) Å, c=14.4102(13) Å, V=2861.0(4) Å{sup 3}. The structure features infinite chains of [Ga{sub 2}Sb{sub 2}S{sub 11}{sup 10–}]{sub ∞} propagating along a direction separated by Ce{sup 3+} cations and S{sup 2−} anions. La{sub 2}Ga{sub 0.33}SbS{sub 5} adopts the family of La{sub 4}FeSb{sub 2}S{sub 10}-related structure with a=7.5193(6) Å, c=13.4126(17) Å, V=758.35(13) Å{sup 3}. Its structure is built up from the alternate stacking of La/Sb/S and La/Ga/S 2D building blocks. The La/Sb/S slabs consist of teeter-totter chains of Sb1S{sub 4} seesaws, which are connected via sharing the apexes of μ{sub 4}-S1. Moreover, La1 is positionally disordered with Sb1 and stabilized in a bicapped trigonal prismatic coordination sphere. Between these La/Sb/S slabs, La2S{sub 8} square antiprisms are connected via edge-sharing into 2D building blocks, creating tetrahedral sites partially occupied by the Ga1 atoms. UV/Vis diffuse reflectance spectroscopy study shows that the optical gap of La{sub 2}Ga{sub 0.33}SbS{sub 5} is about 1.76 eV. - Graphical abstract: Two new quaternary sulfides La{sub 2}Ga{sub 0.33}SbS{sub 5} and Ce{sub 4}GaSbS{sub 9} have been prepared by solid-state reactions. Ce{sub 4}GaSbS{sub 9} crystallizes in RE{sub 4}GaSbS{sub 9} (RE=Pr, Nd, Sm, Gd–Ho) structure type, while La{sub 2}Ga{sub 0.33}SbS{sub 5} belongs to the family of La{sub 4}FeSb{sub 2}S{sub 10}-related structure and exhibits an optical gap of 1.76 eV. - Highlights: • Two new quaternary sulfides La{sub 2}Ga{sub 0.33}SbS{sub 5} and Ce{sub 4}GaSbS{sub 9} have been prepared by solid-state reaction. • Ce{sub 4}GaSbS{sub 9} crystallizes in RE{sub 4}GaSbS{sub 9} (RE=Pr, Nd, Sm, Gd–Ho) structure type, while La{sub 2}Ga{sub 0.33}SbS{sub 5} belongs to the family of La{sub 4}FeSb{sub 2}S{sub 10}-related structure. • The optical gap of 1.76 eV for La{sub 2}Ga{sub 0.33}SbS{sub 5} was deduced from UV/Vis reflectance spectroscopy.

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

Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl: A rare example of Ti(IV) in a square pyramidal oxygen coordination

A new oxychloride Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl has been synthesized using the solid state method. Its crystal and magnetic structure was investigated in the 1.5–550 K temperature range using electron diffraction, high angle annular dark field scanning transmission electron microscopy, atomic resolution energy dispersive X-ray spectroscopy, neutron and X-ray powder diffraction. At room temperature Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl crystallizes in the P4/mmm space group with the unit cell parameters a=3.91803(3) Å and c=19.3345(2) Å. Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl is a new n=4 member of the oxychloride perovskite-based homologous series A{sub n+1}B{sub n}O{sub 3n−1}Cl. The structure is built of truncated Pb{sub 3}Fe{sub 3}TiO{sub 11} quadruple perovskite blocks separated by CsCl-type Pb{sub 2}Cl slabs. The perovskite blocks consist of two layers of (Fe,Ti)O{sub 6} octahedra sandwiched between two layers of (Fe,Ti)O{sub 5} square pyramids. The Ti{sup 4+} cations are preferentially located in the octahedral layers, however, the presence of a noticeable amount of Ti{sup 4+} in a five-fold coordination environment has been undoubtedly proven using neutron powder diffraction and atomic resolution compositional mapping. Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl is antiferromagnetically ordered below 450(10) K. The ordered Fe magnetic moments at 1.5 K are 4.06(4) μ{sub B} and 3.86(5) μ{sub B} on the octahedral and square-pyramidal sites, respectively. - Highlights: • Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl has been synthesized using the solid state method. • The structure has been refined using neutron powder diffraction data at 1.5–550 K. • It is a new n=4 member of the perovskite-related homologous series A{sub n+1}B{sub n}O{sub 3n−1}Cl. • Ti{sup 4+} cations have both octahedral and square-pyramidal coordination environment. • Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl is antiferromagnetically ordered below T{sub N}≈450 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2013

Recent Enhancements to the NASA Langley Structural Acoustics Loads and Transmission (SALT) Facility

The Structural Acoustics Loads and Transmission (SALT) facility at the NASA Langley Research Center is comprised of an anechoic room and a reverberant room, and may act as a transmission loss suite when test articles are mounted in a window connecting the two rooms. In the latter configuration, the reverberant room acts as the noise source side and the anechoic room as the receiver side. The noise generation system used for qualification testing in the reverberant room was previously shown to achieve a maximum overall sound pressure level of 141 dB. This is considered to be marginally adequate for generating sound pressure levels typically required for launch vehicle payload qualification testing. Recent enhancements to the noise generation system increased the maximum overall sound pressure level to 154 dB, through the use of two airstream modulators coupled to 35 Hz and 160 Hz horns. This paper documents the acoustic performance of the enhanced noise generation system for a variety of relevant test spectra. Additionally, it demonstrates the capability of the SALT facility to conduct transmission loss and absorption testing in accordance with ASTM and ISO standards, respectively. A few examples of test capabilities are shown and include transmission loss testing of simple unstiffened and built up structures and measurement of the diffuse field absorption coefficient of a fibrous acoustic blanket.

Rizzi, Stephen A.↗
DOE OSTI2024

Perovskite Grown in Gallium Nitride Nanowire Matrix for Stable and High‐Efficiency X‐Ray Detection

High-quality quasi-2D perovskites in a GaN nano-wire matrix are grown to build a 3D hetero-structure for high-performance X-ray sensing. In the 3D hetero-structure, GaN nano-wire matrix serves as an n-type charge collector that can rapidly extract carriers through the bulk film of the perovskite layer. Together with a p-type top electrode, a p–i–n diode with the 3D hetero-structure is built, that exhibits a rectified current–voltage characteristic. After analyzing the interface energy alignment, it is found that the fermi levels of the perovskite and GaN are aligned in the dark, and a quasi-fermi level splits upon illumination, introducing a built-in electrical field at the interface. As a result, strong photo-induced current is observed from the diode without an external field. Finally, the 3D diode for X-ray detection demonstration is used, revealing a sensitivity of 308.9 µC Gy air -1 cm -2 at an exceptionally low applied field of 0.125 V µm -1 . The X-ray-induced signal from the 3D diode is stable after 155 cycles of X-ray irradiation under a constant electric field. This demonstration informs a new 3D architecture for high-performance X-ray sensing, and it shows that GaN is a robust n-type interface for perovskite optoelectronic devices.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

SLS Integrated Modal Test Uncertainty Quantification using the Hybrid Parametric Variation Method

Uncertainty in structural loading during launch is a significant concern in the development of spacecraft and launch vehicles. Small variations in launch vehicle and payload mode shapes and their interaction can result in significant variation in system loads. In many cases involving large aerospace systems it is difficult, not economical, or impossible to perform a system modal test. However, it is still vital to obtain test results that can be compared with analytical predictions to validate models. Instead, the “Building Block Approach” is used in which system components are tested individually. Component models are correlated and updated to agree as best they can with test results. The Space Launch System consists of a number of components that are assembled into a launch vehicle. Finite element models of the components are developed, reduced to Hurty/Craig-Bampton models and assembled to represent different phases of flight. The only opportunity to obtain modal test data from an assembled Space Launch System will be during the Integrated Modal Test. There is always uncertainty in every model, which flows into uncertainty in predicted system results. Uncertainty Quantification is used to determine statistical bounds on prediction accuracy based on model uncertainty. For the Space Launch System, model uncertainty is at the Hurty/Craig-Bampton component level. Uncertainty in the Hurty/Craig-Bampton components is quantified using the hybrid parametric variation approach that combines parametric and nonparametric uncertainty. Uncertainty in model form is one of the biggest contributors to uncertainty in complex built-up structures. This type of uncertainty cannot be represented by variations infinite element model input parameters and thus cannot be included in a parametric approach. However, model-form uncertainty can be modeled using a nonparametric approach based on random matrix theory. The hybrid parametric variation method requires the selection of dispersion values for the Hurty/Craig-Bampton fixed-interface eigenvalues, and the Hurty/Craig-Bampton stiffness matrices. Component test/analysis frequency error is used to identify the fixed-interface eigenvalue dispersions, while test/analysis cross-orthogonality is used to identify stiffness dispersion values. The hybrid parametric variation uncertainty quantification approach is applied to the Space Launch System Integrated Modal Test configuration. Monte Carlo analysis is performed, and statistics are determined for modal correlation metrics, frequency response from Integrated Modal Test shakers to selected accelerometers, as well as other metrics for determining how well target modes are excited and identified. If the predicted uncertainty envelopes future Integrated Modal Test results, then there will be increased confidence in the utility of the component-based hybrid parametric variation uncertainty quantification approach.

Uncertainty Quantification↗
NASA NTRS1994

Associated with aerospace vehicles development of methodologies for the estimation of thermal properties

Thermal stress analyses are an important aspect in the development of aerospace vehicles at NASA-LaRC. These analyses require knowledge of the temperature distributions within the vehicle structures which consequently necessitates the need for accurate thermal property data. The overall goal of this ongoing research effort is to develop methodologies for the estimation of the thermal property data needed to describe the temperature responses of these complex structures. The research strategy undertaken utilizes a building block approach. The idea here is to first focus on the development of property estimation methodologies for relatively simple conditions, such as isotropic materials at constant temperatures, and then systematically modify the technique for the analysis of more and more complex systems, such as anisotropic multi-component systems. The estimation methodology utilized is a statistically based method which incorporates experimental data and a mathematical model of the system. Several aspects of this overall research effort were investigated during the time of the ASEE summer program. One important aspect involved the calibration of the estimation procedure for the estimation of the thermal properties through the thickness of a standard material. Transient experiments were conducted using a Pyrex standard at various temperatures, and then the thermal properties (thermal conductivity and volumetric heat capacity) were estimated at each temperature. Confidence regions for the estimated values were also determined. These results were then compared to documented values. Another set of experimental tests were conducted on carbon composite samples at different temperatures. Again, the thermal properties were estimated for each temperature, and the results were compared with values obtained using another technique. In both sets of experiments, a 10-15 percent off-set between the estimated values and the previously determined values was found. Another effort was related to the development of the experimental techniques. Initial experiments required a resistance heater placed between two samples. The design was modified such that the heater was placed on the surface of only one sample, as would be necessary in the analysis of built up structures. Experiments using the modified technique were conducted on the composite sample used previously at different temperatures. The results were within 5 percent of those found using two samples. Finally, an initial heat transfer analysis, including conduction, convection and radiation components, was completed on a titanium sandwich structural sample. Experiments utilizing this sample are currently being designed and will be used to first estimate the material's effective thermal conductivity and later to determine the properties associated with each individual heat transfer component.

Scott, Elaine P.↗
DOE OSTI2019

High Nuclearity Uranyl Cages Using Rigid Aryl Phosphonate Ligands

Two high nuclearity uranyl cages were crystallized in high yield under mild solvothermal conditions using rigid aryl phosphonate ligands. These compounds are prepared either through an in situ phosphonate ligand condensation reaction or via serendipitous assembly with a bulky phosphonate ligand. Firstly, the flexibility of the phosphonate ligands enhances the curvature of the uranyl polyhedra in the assembly of both compounds. Secondly, the formation of bent pyrophosphonate ligands through temperature and solvent-driven in situ ligand synthesis is crucial for the assembly of UPhPO 3 . Thirdly, the serendipitous assembly of UPh 2 CPO 3 is favored by the use of sterically hindered bulky phosphonate ligands. The overall structure of UPhPO 3 consists of 16 uranyl cations that are coordinated by phenyl phosphonate and pyrophosphonate ligands while UPh 2 CPO 3 structure is built from uranyl dimers and bulky fluorenyl phosphonate ligand to yield a 12 membered cage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

An experimental investigation of the effectiveness of Ar-CO 2 shielding gas mixture for the wire arc additive process

Wire arc additive manufacturing (AM) is the process by which a large, metallic structure is built layer-by-layer using a welding arc to melt a wire feedstock. A novel opportunity exists to alter the shielding gas composition to fabricate distinct geometrical features without altering the other AM parameters. In this paper, shielding gases with varied concentrations of Argon (Ar) and CO 2 was used to deposit three distinct geometric shapes (walls, infill, and overhang) using a wire-based additive manufacturing system utilizing the gas metal arc welding (GMAW) surface tension transfer (STT) process. Computer-aided design (CAD) models were sliced with a custom-built slicer, and the sliced algorithm was converted into optimal robotic toolpaths. A custom virtual instrument (VI) was built in LabVIEW to compare the temperature profiles on the surface during each deposition process. After each deposition, the geometric features were scanned, and the surface waviness value was evaluated. Tensile and Charpy impact coupons were extracted from the wall geometries in the longitudinal and transverse directions and tested. The results indicated that a higher CO 2 content produced higher melt pool temperatures to an extent, while lower contents of CO 2 resulted in a dimensionally accurate geometry. The data also indicated that the 2%/98% CO 2 /Ar blend produced scatter in tensile strength and the analysis of variance (ANOVA) shows significant difference. However, the intermediate range of CO 2 (5–10%) resulted in uniform tensile properties. Altogether, these results indicate that a 5%/95% CO 2 /Ar blend is the ideal shielding gas for lowering process temperatures and improving mechanical properties in wire arc additive manufacturing using the gas metal arc welding surface tension transfer process. Additionally, varying concentrations of Ar/CO 2 can be used within the same part in order to modify the local properties or process parameters such as strength, toughness, temperature, or dimensional features. This may improve overall manufacturing quality without sacrificing specific properties.

42 ENGINEERING↗
DOE OSTI2022

Urbanization Impact on Regional Climate and Extreme Weather: Current Understanding, Uncertainties, and Future Research Directions

Abstract Urban environments lie at the confluence of social, cultural, and economic activities and have unique biophysical characteristics due to continued infrastructure development that generally replaces natural landscapes with built-up structures. The vast majority of studies on urban perturbation of local weather and climate have been centered on the urban heat island (UHI) effect, referring to the higher temperature in cities compared to their natural surroundings. Besides the UHI effect and heat waves, urbanization also impacts atmospheric moisture, wind, boundary layer structure, cloud formation, dispersion of air pollutants, precipitation, and storms. In this review article, we first introduce the datasets and methods used in studying urban areas and their impacts through both observation and modeling and then summarize the scientific insights on the impact of urbanization on various aspects of regional climate and extreme weather based on more than 500 studies. We also highlight the major research gaps and challenges in our understanding of the impacts of urbanization and provide our perspective and recommendations for future research priorities and directions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Geometry-Induced Spatial Variation of Microstructure Evolution During Selective Electron Beam Melting of Rene-N5

High gamma prime (γ') nickel-based alloys produced by selective electron beam melting are of interest to the turbine industry which requires control of microstructure in relation to loading conditions within complex component geometry. Welding literature predicts cracking and microstructure evolution as a function of alloy composition and process parameters in this class of alloys. In addition, Additive manufacturing causes variations in the above conditions due to the interaction of geometry on processing and heat transfer. The influence of geometry on processing conditions was explored for alloy Rene N5 by characterizing the solidification grain microstructure and solid-state precipitation. A Semi-Analytical Heat Transfer Model was employed to explain the resulting variation in solidification grain morphology that occurred due to the part geometry. Finally, the as-built precipitation structure was found to vary as a function of build height and had no correlation to the solidification grain structure or the layer geometry.

36 MATERIALS SCIENCE↗
DOE OSTI2014

F{sup −}/OH{sup −} substitution in [H{sub 4}tren]{sup 4+} and [H{sub 3}tren]{sup 3+} hydroxyfluorotitanates(IV) and classification of tren cation configurations

Three [H{sub 3}tren]{sup 3+} or [H{sub 4}tren]{sup 4+} hydroxyfluorotitanates(IV) are solvothermally synthesized from TiO{sub 2}, tren amine, 40% HF aqueous solution and ethanol under microwave heating at 120 °C and 190 °C. [H{sub 4}tren]·(TiF{sub 4.6}(OH){sub 1.4}){sub 2}·2.7H{sub 2}O (I) and β-[H{sub 3}tren]·(TiF{sub 4.5}(OH){sub 1.5})·(F) (II) are described for the first time. The third compound, α-[H{sub 3}tren]·(TiF{sub 4.7}(OH){sub 1.3})·(F) (III), was previously reported as a pure fluorotitanate. The structure determinations are performed from single crystal (I) and powder (II) X-ray diffraction data. The F{sup −}/OH{sup −} substitution, expected from the presence of water in the reaction medium, is characterized by chemical analyses and {sup 19}F MAS solid state NMR experiments: all three structures are built up from Ti(F,OH){sub 6}{sup 2−} octahedra and “free” fluoride ions or water molecules. “Free” fluoride ions are not affected by F{sup −}/OH{sup −} substitution. The electroneutrality is ensured by triprotonated or tetraprotonated tren amines which adopt specific configurations. Additionally, based on the analysis of [H{sub 3}tren]{sup 3+} or [H{sub 4}tren]{sup 4+} hydroxo/oxo/fluorometalates, a classification of the configurations of tren cations is proposed. - Graphical abstract: The ratio of the relative intensities of the {sup 19}F NMR lines assigned to F atoms belonging to isolated TiF{sub 6−x}(OH){sub x} octahedra and to “free” fluoride ions shows that the F{sup −}/OH{sup −} substitution concerns only F atoms bonded to titanium. - Highlights: • Three tren templated hydroxyfluorotitanates(IV) have been solvothermally synthesized. • They are built up from Ti(F,OH){sub 6}{sup 2−} octahedra and “free” F{sup −} ions or H{sub 2}O molecules. • F{sup −}/OH{sup −} substitution does not affect “free” F{sup −} sites. • [H{sub 4}tren]{sup 4+} and [H{sub 3}tren]{sup 3+} cations adopt specific configurations. • A classification of the configurations of tren cations is proposed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Pyrophosphates AMoP2O7 (A = Li and Na): Synthesis, structure and electrochemical properties

Highlights: • Carbon-coated pyrophosphate materials AMoP2O7 (A = Li and Na) were prepared via freeze- drying method. • BVEL analysis revealed the remarkable difference in the alkali diffusion behaviors of two AMoP{sub 2}O{sub 7} polymorphs. • LiMoP{sub 2}O{sub 7} shows the superior electrochemical activity towards de/intercalation of Li{sup +} and Na{sup +} ions compared with NaMoP{sub 2}O{sub 7} - Abstract: The carbon-coated single-phase samples of the pyrophosphates AMoP{sub 2}O{sub 7} (A = Li and Na) were synthesized using freeze-drying followed by annealing in a sealed silica tube with the Fe/FeO getter. The Rietveld refinement of the X-Ray powder diffraction data proved both structures are built up as a network of corner-linked MoO{sub 6} octahedra and P{sub 2}O{sub 7} groups with A-cations located in the open tunnels running along the [100] (LiMoP{sub 2}O{sub 7}) and [101] (NaMoP{sub 2}O{sub 7}) directions. The bond valence energy landscapes (BVEL) analysis revealed three-dimensional pathways of alkali-ion migration with significantly different activation energies (0.8 eV for LiMoP{sub 2}O{sub 7} and 4.5 eV for NaMoP{sub 2}O{sub 7}) anticipating LiMoP{sub 2}O{sub 7} to exhibit faster Li{sup +} diffusion and better electrochemical characteristics. Both materials displayed electrochemical activity in Li- and Na-cells with reversible capacities of ∼20 mA h g{sup −1} for NaMoP{sub 2}O{sub 7} and more than 70 mA h g{sup −1} for LiMoP{sub 2}O{sub 7}, being in a good agreement with the BVEL results.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Additive manufacturing of Zr-based metallic glass structures on 304 stainless steel substrates via V/Ti/Zr intermediate layers

Welding of dissimilar metals is challenging, particularly between crystalline metals and metallic glasses (MGs). Here in this study, Zr 65.7 Cu 15.6 Ni 11.7 Al 3.7 Ti 3.3 (wt%) MG structures were built on 304 stainless steel (SS) substrates by laser-foil-printing (LFP) additive manufacturing technology in which MG foils were laser welded layer-by-layer onto the SS substrate with a transition route, i.e., SS → V → Ti → Zr → MG. The direct welding of MG on SS would lead to the formation of various brittle intermetallics and the consequent peeling off of the welded MG foils from the SS substrate, which could be resolved via the use of V/Ti/Zr intermediate layers. The chemical composition, formed phases, and micro-hardness were characterized in the dissimilar joints by energy dispersive spectroscopy, X-ray diffraction, and micro-indentation. Since the intermediate materials were highly compatible with the base metals or the adjacent intermediate metals, undesirable intermetallics were not detected in the dissimilar joint. The bonding tensile strength between the SS substrate and the MG part with intermediate layers was measured about 477 MPa.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Long- and Short-Range Constraints for the Structure Determination of Layered Silicates with Stacking Disorder

Layered silicates have important applications as host materials, supports for catalysis, and zeolite precursors. However, their local structures are often challenging to establish due to disorder of the sheet assemblies. We present a new protocol that combines long- and short-range structural constraints from diffraction and solid-state NMR techniques, respectively, to determine the molecular structure of layered silicates in the presence of various extents of stacking disorder. Solid-state 29Si NMR data are largely insensitive to the incomplete extent of three-dimensional (3D) crystallinity that limits the interpretation of diffraction data alone to the identification of possible unit cells and space groups. State-of-the-art NMR crystallography techniques consequently provide a simplified view of materials from which candidate framework structures can be built and evaluated based on local structural constraints, including interatomic distances, Si site numbers and multiplicities, and Si–O–Si connectivities, and refined using density functional theory. This protocol was applied to a new layered silicate material named CLS-1, of composition [Si5O11H][C9N2H15]·1.9(H2O), synthesized by using a fluoride-based protocol and cationic alkylaminopyridinium as a structure-directing agent (SDA). Despite the intrinsic complexity and partial ordering of the intersheet arrangements and organic–inorganic interactions, this led to the identification of a single space group that is compatible with both NMR and diffraction data, from which the silicate framework structure could be established,. The remarkable similarities between the layered framework structures of CLS-1, HUS-2 (Tsunoji et al. J. Mater. Chem.2012, 22, 13682), and another layered silicate material with a radically different morphology and extent of stacking order and interlayer dynamics, established by using a similar approach (Brouwer et al. J. Am. Chem. Soc.2013, 135, 5641), point to the remarkable robustness of this previously unknown silicate framework type.

Cadars, Sylvian↗
DOE OSTI2019

Designed asymmetric coordination helicates with bis-β-diketonate ligands

A new bis-(β-diketone) ligand featuring built-up structural asymmetry yields non-symmetric Fe(III) and Ga(III) dinuclear, triple-stranded helicates by design. Their structural properties have been studied, both in solid state and in solution, and compared with their corresponding symmetric analogues. Finally, the robustness observed shows the potential of this synthetic strategy to develop non-symmetric helicoidal motifs with specific functional groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗