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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Metal-containing ionic liquid-based, uncharged–charged diblock copolymers that form ordered, phase-separated microstructures and reversibly coordinate small protic molecules

A metal-containing ionic liquid-based, uncharged-charged block copolymer (BCP) system made via RAFT polymerization is presented. Small-angle X-ray scattering studies show these Co(II) bis(salicylate) anion-containing BCPs can form ordered microstructures (including a gyroid phase) in their neat states. Additionally, these BCPs can reversibly coordinate H 2 O or small alcohols with a noticeable color change.

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

Light-Controlled Hierarchical Self-Assembly of Polyelectrolytes and Supramolecular Polymers

Dynamic control over supramolecular interactions using various stimuli continues to drive the development of smart materials. In this paper, we describe the extension of dynamic self-assembly to a self-assembled hierarchical structure. A peptide amphiphile (PA) was designed with a photocleavable nitrobenzyl ester component such that it would undergo a sphere-to-cylinder transition upon irradiation, as confirmed by cryogenic transmission electron microscopy and small-angle X-ray scattering (SAXS). The photocleavable PA was then tested in the formation of a macroscopic sac made through a complex hierarchical self-assembly process between PA and hyaluronic acid. The microstructure of the resulting sac has previously been noted to depend dramatically on the geometry of the PA nanostructure. Photolysis of the PA solution during sac formation led to a sac microstructure that displayed characteristics of sacs made with both cylinder-forming PAs and sphere-forming PAs, as measured by scanning electron microscopy and SAXS.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Silicon Microwire Arrays for Solar Energy-Conversion Applications

Highly structured silicon microwire (Si MW) arrays have been synthesized and characterized as absorbers for solar energy-conversion systems. These materials are of great interest for applications in solar energy conversion, including solar electricity and solar fuels production, due to their unique materials properties, form factors, ease of fabrication, and device processing attributes. The Si MW array geometry allows for efficient collection of photogenerated carriers from impure materials that have short minority-carrier diffusion lengths, while simultaneously allowing for high optical absorption and high external quantum yields for charge carrier collection. In addition, Si MW arrays exhibit unique mesoscale optical behavior and can be removed from the growth substrate to provide flexible, processable arrays of Si microwires ordered in a variety of organic polymers and ionomers. The unique photon management properties of Si MW arrays, combined with their high internal surface area and controlled morphology for catalyst placement and support, allow for the use of earth-abundant electrocatalysts to produce an integrated, functional photoelectrode. Furthermore, these materials therefore also provide an opportunity to explore the 3-dimensional photoelectrochemical behavior of fuel-forming microstructured electrodes.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

ZIF-8 Membrane Separation Performance Tuning by Vapor Phase Ligand Treatment

Vapor phase ligand treatment (VPLT) of 2-aminobenzimidazole (2abIm) for 2-methylimidazole (2mIm) in ZIF-8 membranes prepared by two different methods (LIPS: ligand induced permselectivation and RTD: rapid thermal deposition) results in a notable shift of the molecular level cut-off to smaller molecules establishing selectivity improvements from ca. 1.8 to 5 for O 2 /N 2 ; 2.2 to 32 for CO 2 /CH 4 ; 2.4 to 24 for CO 2 /N 2 ; 4.8 to 140 for H 2 /CH 4 and 5.2 to 126 for H 2 /N 2 . Furthermore, stable (based on a one-week test) oxygen-selective air separation performance at ambient temperature, 7 bar(a) feed, and 1 bar(a) sweep-free permeate with a mixture separation factor of 4.5 and oxygen flux of 2.6×10 -3 mol m -2 s -1 is established. LIPS and RTD membranes exhibit fast and gradual evolution upon a 2abIm-VPLT, respectively, reflecting differences in their thickness and microstructure. Functional reversibility is demonstrated by showing that the original permeation properties of the VPLT-LIPS membranes can be recovered upon 2mIm-VPLT.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Effects of surface chemistry and microstructure of electrolyte on oxygen reduction kinetics of solid oxide fuel cells

In this study, we report systematic investigation of the surface properties of yttria-stabilized zirconia (YSZ) electrolytes with the control of the grain boundary (GB) density at the surface, and its effects on electrochemical activities. The GB density of thin surface layers deposited on single crystal YSZ substrates is controlled by changing the annealing temperature (750-1450 °C). Higher oxygen reduction reactions (ORR) kinetics is observed in samples annealed at lower temperatures. The higher ORR activity is ascribed to the higher GB density at the YSZ surface where 'mobile' oxide ion vacancies are more populated. Meanwhile, oxide ion vacancies concurrently created with yttrium segregation at the surface at the higher annealing temperature are considered inactive to oxygen incorporation reactions. Our results provide additional insight into the interplay between the surface chemistry, microstructures, and electrochemical activity. They potentially provide important guidelines for engineering the electrolyte electrode interfaces of solid oxide fuel cells for higher electrochemical performance.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe 2 O 4 , referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe 2–x Mo x O 4 , referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7 g/cm 3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo 4+ ) for higher x while in a mixed chemical valence state (Mo 4+ , Mo 5+ , Mo 6+ ) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behavior including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field ( H c ) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent H c is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Investigation of Cathode Electrocatalytic Activity using Surface Engineered Thin Film Samples and High Temperature Physical Property Measurements

In this Final Technical Report, a summary of the technical output from the award DE-NT0004105 is given. First, the major goals and observations from the project are reviewed and then specific example results are presented as highlights. The surprising importance of microstructure on the surface chemical exchange coefficient in La 0.7 Sr 0.3 MnO 3 (LSM) was uncovered in this work and is re-emphasized in this report. Significant orientation and thickness dependencies of the surface exchange coefficient are correlated with microstructural effects, especially to the nature of the strain, dislocation content, and grain boundary population. We also illustrate similar microstructural effects are present in other SOFC cathode systems, including LSCF (La 1-x SrxCo 1-y Fe y O 3 ) and La 2 NiO 4 (LNO). Throughout the report, the relation to SOFC cathode performance is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A Case Study of Multimodal, Multi-institutional Data Management for the Combinatorial Materials Science Community

Although the convergence of high-performance computing, automation, and machine learning has significantly altered the materials design timeline, transformative advances in functional materials and acceleration of their design will require addressing the deficiencies that currently exist in materials informatics, particularly a lack of standardized experimental data management. The challenges associated with experimental data management are especially true for combinatorial materials science, where advancements in automation of experimental workflows have produced datasets that are often too large and too complex for human reasoning. The data management challenge is further compounded by the multimodal and multi-institutional nature of these datasets, as they tend to be distributed across multiple institutions and can vary substantially in format, size, and content. Furthermore, modern materials engineering requires the tuning of not only composition but also of phase and microstructure to elucidate processing–structure–property–performance relationships. To adequately map a materials design space from such datasets, an ideal materials data infrastructure would contain data and metadata describing (i) synthesis and processing conditions, (ii) characterization results, and (iii) property and performance measurements. In this work, we present a case study for the low-barrier development of such a dashboard that enables standardized organization, analysis, and visualization of a large data lake consisting of combinatorial datasets of synthesis and processing conditions, X-ray diffraction patterns, and materials property measurements generated at several different institutions. While this dashboard was developed specifically for data-driven thermoelectric materials discovery, we envision the adaptation of this prototype to other materials applications, and, more ambitiously, future integration into an all-encompassing materials data management infrastructure.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Ptychography of Organic Thin Films at Soft X-ray Energies

Organic photovoltaics (OPV) are a sustainable and inexpensive source of energy comprised of a mixture of an electron-donating and an electron-accepting material (often a polymer and fullerene derivative, respectively) to create a bulk heterojunction (BHJ). However, these devices are held back by low efficiencies. Improving the efficiency in a systematic way requires a comprehensive understanding of the device function and microstructure, but directly imaging the subsurface active layer structure is challenging. Here we demonstrate that ptychography may be used to image the OPV active layer with good film stability and materials contrast in both polymer:fullerene and all-polymer BHJ films. This is possible using soft X-ray ptychography available at the Advanced Light Source beamline 5.3.2.1. We achieve a resolution of 30–50 nm with no discernible radiation damage and discuss the potential for further improvements. This characterization technique could complement widely used electron microscopy and soft X-ray scattering.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2019

PNNL's Intermediate Characterization Summary for the MP-1 Experiment

Characterization of the as-fabricated fuel is being performed at Pacific Northwest National Laboratory (PNNL) in accordance with Characterization Plan for the Fabrication of U-10Mo for the MP-1 Experiment, hereinafter the MP-1 Characterization Plan. Similar characterization work is also being performed at two other organizations, INL and Los Alamos National Laboratory, to provide a detailed understanding of the as-fabricated fuel that would be irradiated in the MP-1 experiment. Under the MP 1 Characterization Plan, fuel foils with different fabrication parameters (such as rolling condition, rolling thickness reduction, co-rolling with Zr layers) are being studied. Similar samples from master foils were sent to each of the three organizations, so that testing and analysis can be performed independently using similar equipment and a standardized set of measurement and analysis procedures. A final consolidated report will be prepared based on this work and it will summarize all of the information obtained from different labs. The MP-1 experiment will provide an opportunity to understand the effects of processing conditions on the final fuel microstructure, to compare results obtained independently, and achieve a three-way validation. Currently, PNNL characterized 28 U-10Mo samples, by sectioning six pieces/specimens from each sample/foil, in accordance with the MP-1 Characterization Plan. These 28 samples consist of six types of MP-1 characterization foils from BWXT: 0.047 in. thick hot-rolled samples with and without Zr layers; 0.02 in. thick cold-rolled and annealed samples with and without Zr layers, and 0.01 in. thick cold-rolled and annealed samples with and without Zr layers. During the first year, PNNL completed sectioning of two subsamples per sample/foil and performed the necessary characterization on all 28 U-10Mo samples. This report covers the results of the first year’s analyses of PNNL’s MP-1 fuel characterization samples. Microstructure, chemical composition, carbide morphology, U-10Mo foil thickness, Zr thickness, mechanical properties (microhardness), and density were evaluated in both longitudinal and transverse directions for foils of the three different thicknesses.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Nanointerface-driven reversible hydrogen storage in the nanoconfined Li-N-H system

Internal interfaces in the Li 3 N/[LiNH 2 + 2LiH] solid-state hydrogen storage system alter the hydrogenation and dehydrogenation reaction pathways upon nanosizing, suppressing undesirable intermediate phases to dramatically improve kinetics and reversibility. Finally, the key role of solid interfaces in determining thermodynamics and kinetics suggests a new paradigm for optimizing complex hydrides for solid-state hydrogen storage by engineering internal microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Simulation-guided analysis of resonant soft X-ray scattering for determining the microstructure of triblock copolymers

Resonant soft X-ray scattering (RSoXS) probes structure with chemical sensitivity that is useful for determining the morphology of multiblock copolymers. However, the hyperspectral scattering data produced by this technique can be challenging to interpret. Here, in this study, we use computational scattering simulations to extract the microstructure of a model triblock copolymer from the energy-dependent scattering from RSoXS. An ABC triblock terpolymer formed from poly(4-methylcaprolactone) (P4MCL), poly(2,2,2-trifluoroethylacrylate) (PTFEA), and poly (dodecylacrylate) (PDDA), P4MCL-block-PTFEA-block-PDDA, was synthesized as the model triblock system. Through quantitative evaluation of simulated scattering data from a physics-informed set of candidate structure models against experimental RSoXS data, we find the best agreement with hexagonally packed core–shell cylinders. This result is also consistent with electron-density reconstruction from hard X-ray scattering data evaluated against electron-density maps generated with the same model set. These results demonstrate the utility of simulation-guided scattering analysis to study complex microstructures that are challenging to image by microscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2003

Prebiotic Synthesis of Autocatalytic Products From Formaldehyde-Derived Sugars as the Carbon and Energy Source

Our research objective is to understand and model the chemical processes on the primitive Earth that generated the first autocatalytic molecules and microstructures involved in the origin of life. Our approach involves: (a) investigation of a model origin-of-life process named the Sugar Model that is based on the reaction of formaldehyde- derived sugars (trioses and tetroses) with ammonia, and (b) elucidation of the constraints imposed on the chemistry of the origin of life by the fixed energies and rates of C,H,O-organic reactions under mild aqueous conditions. Recently, we demonstrated that under mild aqueous conditions the Sugar Model process yields autocatalytic products, and generates organic micropherules (2-20 micron dia.) that exhibit budding, size uniformity, and chain formation. We also discovered that the sugar substrates of the Sugar Model are capable of reducing nitrite to ammonia under mild aqueous conditions. In addition studies done in collaboration with Sandra Pizzarrello (Arizona State University) revealed that chiral amino acids (including meteoritic isovaline) catalyze both the synthesis and specific handedness of chiral sugars. Our systematic survey of the energies and rates of reactions of C,H,O-organic substrates under mild aqueous conditions revealed several general principles (rules) that govern the direction and rate of organic reactions. These reactivity principles constrain the structure of chemical pathways used in the origin of life, and in modern and primitive metabolism.

Weber, Arthur L.↗
DOE OSTI2018

3D-Printed Hydrogel Composites for Predictive Temporal (4D) Cellular Organizations and Patterned Biogenic Mineralization

Materials chemistries for hydrogel scaffolds that are capable of programming temporal (4D) attributes of cellular decision-making in supported 3D microcultures are described. The scaffolds are fabricated using direct-ink writing (DIW)-a 3D-printing technique using extrusion to pattern scaffolds at biologically relevant diameters (<= 100 mu m). Herein, DIW is exploited to variously incorporate a rheological nanoclay, Laponite XLG (LAP), into 2-hydroxyethyl methacrylate (HEMA)-based hydrogels-printing the LAP-HEMA (LH) composites as functional modifiers within otherwise unmodified 2D and 3D HEMA microstructures. The nanoclay-modified domains, when tested as thin films, require no activating (e.g., protein) treatments to promote robust growth compliances that direct the spatial attachment of fibroblast (3T3) and preosteoblast (E1) cells, fostering for the latter a capacity to direct long-term osteodifferentiation. Cell-to-gel interfacial morphologies and cellular motility are analyzed with spatial light interference microscopy (SLIM). Through combination of HEMA and LH gels, high-resolution DIW of a nanocomposite ink (UniH) that translates organizationally dynamic attributes seen with 2D gels into dentition-mimetic 3D scaffolds is demonstrated. These analyses confirm that the underlying materials chemistry and geometry of hydrogel nanocomposites are capable of directing cellular attachment and temporal development within 3D microcultures-a useful material system for the 4D patterning of hydrogel scaffolds.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A slice of an aluminum particle: Examining grains, strain and reactivity

The Combustion Institute Micron-scale aluminum (Al) particles are plagued by incomplete combustion that inhibits their reactivity. One approach to improving reactivity is to anneal Al particles to increase dilatational (volumetric) strain which has also been linked to increased combustion performance. While optimal annealing temperatures have been identified (roughly 300 °C), little is known about cooling rate effects on particle combustion performance. This study examines the effect of quenching after annealing Al microparticles to 100, 200 and 300 °C on intra-particle dilatational strain and reactivity. Synchrotron X-ray diffraction analysis of the particles reveals the cooling rates in the range from 0.007 to 0.38 K/s have little effect on the dilatational strain of the aluminum-core, alumina-shell particles. The annealed and quenched Al particles were then combined with a metal oxidizer (copper oxide) to examine reactivity. Flame propagation experiments follow the same trend: flame speeds are unchanged until a critical annealing temperature of 300 °C is reached and performance is maintained for each annealing temperature regardless of cooling rate. These results show that altering the mechanical properties and combustion performance of Al particles is strongly dependent on the annealing temperature and unchanged with variation in cooling rate. The contributions from elastic and plastic deformation mechanisms on strain are also considered and additional experimental results are shown on the microstructure of an Al particle. Focused ion beam milling of an Al particle to electron transparency was combined with transmission electron microscope imaging in order to examine the microstructure of the Al particles. This confirmed that the Al microparticles have a polycrystalline structure shown by grains all exceeding 100 nm in size.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Strain-Induced Shifts in Defective Graphite Phonon Modes Predicted by Density Functional Theory

Carbon fiber composites have gained attention as a structural material because of their high strength-to-weight ratio, and understanding the effect of defects on reactivity and mechanical properties is important for the longevity and safety of the composite. Although it is known that strain causes the underlying graphitic vibrational modes to redshift, it is not clear how strain may alter reactivity and defect-induced vibrational changes. To investigate the strain-induced phonon changes of defective carbon fiber composites, density functional theory calculations of graphite are used, including intercalated hydrogen and fluorine defects. By comparing changes in the bond lengths, formation energies, and phonon density of states for uniaxially and biaxially strained graphite, strain was found to generally make defect formation more favorable and the specific behavior changes are dependent on the strain direction and defect identity. Specifically, intercalated fluorine phonons are more sensitive to strain than hydrogen intercalation phonons, and strain applied along the zigzag direction alters the calculated properties more than strain along the armchair direction. Finally, these results highlight the importance of understanding the microstructural effect of deviations from the ideal material because small changes in strain or defect type can significantly alter the behavior of the carbon fiber composite core.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Static and Dynamic Thermomechanical Properties of Phase-Separated Epoxy Networks with Tuned Microstructures

Here, polymerization-induced phase separation is a useful method for the construction of heterogeneous epoxy networks with properties exceeding their homogeneous counterparts. In this work, we examine the static and dynamic thermomechanical properties of phase-separated epoxy networks salient to their application as encapsulants. Three heterogeneous epoxy-amine networks with nano-, meso-, and macro-phase-separated morphologies comprised of hard and soft domains are compared to a rigid, unstructured network. The glass transition profiles of the heterogeneous networks are complex, spanning many decades in the frequency domain. The nanophase-separated morphology leads to higher coefficient of thermal expansion, yet surprisingly is characterized by reduced residual stress. Under both quasi-static and dynamic compression (strain rates of order 10 –3 and 10 3 s –1 , respectively), the nanophase-separated network also exhibits higher modulus and strength. In split-Hopkinson bar experiments, the energy dissipation characteristics of the epoxy networks were nearly identical. Curiously, however, the Hugoniot response of the macro-phase-separated network determined by ballistic shockwave analysis indicates a remarkable ability of this material to mitigate shockwave propagation in comparison to many homogeneous and heterogeneous polymer materials. Collectively, this work reveals several previously unreported phenomena with respect to structure–property relationships in phase-separated epoxy networks, illustrating the potential value of systematically tuned microstructures for optimization of application-specific physical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Solid electrolyte coated high voltage layered–layered lithium-rich composite cathode: Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2

We find that the electrochemical rate performance and capacity retention of the “layered–layered” lithium rich Li 1.2 Mn 0.525 Ni 0.175 Co 0.1 O 2 (Li-rich NMC) material are significantly improved by a nanometer layer coating of a lithium conducting solid electrolyte, lithium phosphorus oxynitride (LiPON). The LiPON layer is deposited on the Li-rich NMC particles by the RF-magnetron sputtering method. The presence of the LiPON layer provides interfacial stability under high current (rate) and voltage cycling conditions and thereby improves the capacity retention over cycle life compared to pristine or uncoated Li-rich NMC. Specifically, the LiPON coated Li-rich NMC composite electrode showed stable reversible capacities of >275 mAh g -1 when cycled to 4.9 V for more than 300 cycles, and showed at least threefold improvements in the rate performance compared to the uncoated electrode compositions. Increasing the LiPON layer thickness beyond a few nanometers leads to capacity fade due to increasing electronic resistance. Lastly, detailed microstructural and electrochemical impedance spectroscopy studies are undertaken to characterize and understand the role of LiPON in improving the interfacial stability and electrochemical activity at the interface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗