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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Solutions Are the Problem: Ordered Two-Dimensional Covalent Organic Framework Films by Chemical Vapor Deposition

Covalent organic frameworks (COFs) are a promising class of crystalline polymer networks that are useful due to their high porosity, versatile functionality, and tunable architecture. Conventional solution-based methods of producing COFs are marred by slow reactions that produce powders that are difficult to process into adaptable form factors for functional applications, and there is a need for facile and fast synthesis techniques for making crystalline and ordered covalent organic framework (COF) thin films. In this work, we report a chemical vapor deposition (CVD) approach utilizing co-evaporation of two monomers onto a heated substrate to produce highly crystalline, defect-free COF films and coatings with hydrazone, imine, and ketoenamine COF linkages. Further, this all-in-one synthesis technique produces highly crystalline, 40 nm–1 μm-thick COF films on Si/SiO2 substrates in less than 30 min. Crystallinity and alignment were proven by using a combination of grazing-incidence wide-angle X-ray scattering (GIWAXS) and transmission electron microscopy (TEM), and successful conversion of the monomers to produce the target COF was supported by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV–vis measurements. Additionally, we used atomic force microscopy (AFM) to investigate the growth mechanisms of these films, showing the coalescence of triangular crystallites into a smooth film. To show the wide applicability and scope of the CVD process, we also prepared crystalline ordered COF films with imine and ketoenamine linkages. These films show potential as high-quality size exclusion membranes, catalytic platforms, and organic transistors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Designed and biologically active protein lattices

Versatile methods to organize proteins in space are required to enable complex biomaterials, engineered biomolecular scaffolds, cell-free biology, and hybrid nanoscale systems. Here, we demonstrate how the tailored encapsulation of proteins in DNA-based voxels can be combined with programmable assembly that directs these voxels into biologically functional protein arrays with prescribed and ordered two-dimensional (2D) and three-dimensional (3D) organizations. We apply the presented concept to ferritin, an iron storage protein, and its iron-free analog, apoferritin, in order to form single-layers, double-layers, as well as several types of 3D protein lattices. Our study demonstrates that internal voxel design and inter-voxel encoding can be effectively employed to create protein lattices with designed organization, as confirmed by in situ X-ray scattering and cryo-electron microscopy 3D imaging. The assembled protein arrays maintain structural stability and biological activity in environments relevant for protein functionality. The framework design of the arrays then allows small molecules to access the ferritins and their iron cores and convert them into apoferritin arrays through the release of iron ions. The presented study introduces a platform approach for creating bio-active protein-containing ordered nanomaterials with desired 2D and 3D organizations.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Mesocrystal growth through oriented sliding and attachment of nanoplates

Oriented attachment is a critical, yet poorly understood, crystal growth pathway based on the self-assembly of nanocrystals. During oriented attachment, solvent-separated particles align and coalesce through forces that enable precise rotation and translation. While prior studies emphasized intragap forces driving crystallographic alignment, the forces enabling uniform stacking and superlattice formation remain unclear. Here, we demonstrate how macroscopic gibbsite mesocrystals emerge from nanoplates guided into staggered positions by directional sliding. Electron microscopy and X-ray scattering reveal the monoclinic superlattice structure, based on nanoplate stacking with a uniform ≈50° stagger along the gibbsite [010] direction. In situ liquid-cell TEM captures preferential sliding along the gibbsite [010] direction, decelerating with increasing particle overlap. Molecular dynamics simulations reveal that this staggered arrangement corresponds to a global free-energy minimum, rather than full alignment. The simulations also confirm that sliding along the [010] direction is energetically favored and provide insight into the role of interfacial water in achieving long-range ordered assemblies. These insights highlight the energy landscape’s role in oriented attachment, with implications for material synthesis and hierarchical structures in nature.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electron ptychography reveals a ferroelectricity dominated by anion displacements

Sodium niobate, a lead-free ferroic material, hosts delicately balanced, competing order parameters, including ferroelectric states that can be stabilized by epitaxial strain. Here we show that the resulting macroscopic ferroelectricity exhibits an unconventional microscopic structure using multislice electron ptychography. This technique overcomes multiple scattering artefacts limiting conventional electron microscopy, enabling both lateral spatial resolution beyond the diffraction limit and recovery of three-dimensional structural information. These imaging capabilities allow us to separate the ferroelectric interior of the sample from the relaxed surface structure and identify the soft phonon mode and related structural distortions with picometre precision. Unlike conventional ferroelectric perovskites, we find that the polar distortion in this material involves minimal distortions of the cation sublattices and is instead dominated by anion displacements relative to the niobium sublattice. We establish limits on film thickness for interfacial octahedral rotation engineering and directly visualize a random octahedral rotation pattern, arising from the flat dispersion of the associated phonon mode.

ferroelectrics and multiferroics↗
DOE OSTI2023

Tunable thermoplastic elastomer gels derived from controlled-distribution triblock copolymers with crystallizable endblocks

Thermoplastic elastomers (TPEs), a commercially important category of triblock copolymers, are employed alone or upon physical modification with a midblock-selective oil (to form TPE gels, TPEGs) in a broad range of contemporary technologies. While most copolymers in this class of self-networking macromolecules possess glassy polystyrene endblocks and a rubbery polydiene or polyolefin midblock, we investigate TPEGs fabricated from a novel controlled-distribution copolymer with crystallizable polyolefin endblocks and a random-copolymer midblock. According to both electron microscopy and small-angle scattering, the morphologies of these TPEGs remain largely invariant up to 40 wt% oil and then transform considerably at higher oil levels. Although reductions in endblock melting point and crystallinity measured by thermal calorimetry accompany increasing oil content, mechanical properties such as the uniaxial strain at break and fracture toughness improve in some cases by over 50% between 5 and 40 wt% oil. In fact, the strain at break can reach 2500% within this range, thereby confirming that (i) the structure–property relationships of these unique TPEGs are highly composition-tunable and (ii) these TPEGs, stabilized by crystallizable endblocks, provide an attractive alternative for ultrasoft and stretchy recyclable materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Block copolymer self-assembly derived mesoporous magnetic materials with three-dimensionally (3D) co-continuous gyroid nanostructure

Magnetic nanomaterials are gaining interest for their many applications in technological areas from information science and computing to next-generation quantum energy materials. While magnetic materials have historically been nanostructured through techniques such as lithography and molecular beam epitaxy, there has recently been growing interest in using soft matter self-assembly. In this work, a triblock terpolymer, poly(isoprene-block-styrene-block-ethylene oxide) (ISO), is used as a structure directing agent for aluminosilicate sol nanoparticles and magnetic material precursors to generate organic–inorganic bulk hybrid films with co-continuous morphology. After thermal processing into mesoporous materials, results from a combination of small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) are consistent with the double gyroid morphology. Nitrogen sorption measurements reveal a type IV isotherm with H1 hysteresis, and yield a specific surface area of around 200 m 2 g −1 and an average pore size of 23 nm. The magnetization of the mesostructured material as a function of applied field shows magnetic hysteresis and coercivity at 300 K and 10 K. Comparison of magnetic measurements between the mesoporous gyroid and an unstructured bulk magnetic material, derived from the identical inorganic precursors, reveals the structured material exhibits a coercivity of 250 Oe, opposed to 148 Oe for the unstructured at 10 K, and presence of remnant magnetic moment not conventionally found in bulk hematite; both of these properties are attributed to the mesostructure. This scalable route to mesoporous magnetic materials with co-continuous morphologies from block copolymer self-assembly may provide a pathway to advanced magnetic nanomaterials with a range of potential applications.

Chemistry↗
DOE OSTI2023

High- χ diblock copolymers containing poly(vinylpyridine- N -oxide) segments

Block copolymers exhibiting an enhanced segregation strength due to an underlying high Flory–Huggins interaction parameter (high χ) have attracted considerable attention because of their potential of forming microphase-separated domains with very small feature sizes (<10 nm) useful for next-generation lithography. Here, we report the synthesis, characterization, and self-assembly of poly(styrene)- block -poly(2-vinylpyridine N -oxide) (PS- b -P2VPNO) and poly(styrene)- block -poly(4-vinylpyridine N -oxide) (PS- b -P4VPNO) block copolymers. These PS- b -PVPNOs were obtained from the oxidation of their precursors, poly(styrene)- block -poly(2-vinylpyridine) (PS- b -P2VP) and poly(styrene)- block -poly(4-vinylpyridine) (PS- b -P4VP), respectively. The PS- b -PVPNOs exhibit an enhanced segregation as revealed by ordered cylindrical and lamellar structures in the sub-10 nm scale from copolymers with relatively low molecular weight. The morphologies and periodicities of the ordered structures were determined by small-angle X-ray scattering, while atomic-force microscopy was used to image the self-assembly in thin films. Estimates of the changes in disorder–order transition temperature and domain spacing are derived from a theory based on the effects of dipolar interactions. All the experimentally observed morphological changes resulting from the oxidation of P2VP and P4VP precursors can be qualitatively explained in terms of an increased dipole moment of vinylpyridine N -oxide segments. Therefore, our results demonstrate that PVPNO based block copolymers are versatile candidates toward nanopatterned structures with small feature sizes critical for the future microelectronics industry and beyond.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Strong Effect of Nonpolar Solvent Molecular Structure on CdSe Nanoplatelet Stacking

We report a drastic difference in stacking behavior of oleic acid-stabilized 4-monolayer (4 ML) CdSe nanoplatelets (NPLs) in toluene and methylcyclohexane (MCH), two nonpolar solvents that differ in the conformational flexibility of their molecules. Using liquid cell transmission electron microscopy (TEM) and small angle scattering (SAXS) techniques, we show that NPLs form microns-long ribbons consisting of 4 ML CdSe NPLs in toluene, the solvent widely used to form stable colloidal solutions of a broad range of quasi-spherical nanoparticles. In contrast, 4 ML CdSe NPLs are well dispersed in MCH. The difference in stacking behavior of NPLs in toluene and MCH suggests that the conformational flexibility of the solvent molecules, such as the ability to adopt multiple chair conformations, modulates nanoplatelet interactions. Molecular dynamics (MD) simulations reveal that solvent molecules subtly alter the structure of the organic ligand shell. These solvent-dependent changes propagate to the inorganic core, modulating the degree of CdSe nanoplatelet (NPL) twisting and, consequently, the properties of the nanoparticles. We show that toluene better solvates oleate ligands while MCH induces a bimodal oleate span distribution, which can lead to increased solubility of CdSe NPLs. In addition, the solvent can also influence the inorganic core, which, in turn, can modify the nanoparticle properties. We demonstrate that destabilization of toluene solution containing ribbons of 4 ML CdSe NPLs without CdS shells results in the formation of NPL assemblies with amplified spontaneous emission (ASE) with a low threshold of 14 µJ cm−2 that is comparable with that of CdSe/CdS core/shell NPLs. Our results emphasize that the solvent plays a major role in mediating interactions between NPLs and hence their processability for fabrication of functional structures.

CdSe↗
DOE OSTI2023

Super-swelling behavior of stacked lipid bilayer systems

Bilayer systems comprising lipid mixtures are the most well-studied model of biological membranes. While the plasma membrane of the cell is a single bilayer, many intra- and extra-cellular biomembranes comprise stacks of bilayers. Most bilayer stacks in nature are periodic, maintaining a precise water layer separation between bilayers. That equilibrium water separation is governed by multiple inter-bilayer forces and is highly responsive. Biomembranes re-configure inter-bilayer spacing in response to temperature, composition, or mass transport cues. In synthetic bilayer systems for applications in cosmetics or topical treatments, control of the hydration level is a critical design handle. Herein we investigate a binary lipid system that leverages key inter-bilayer forces leading to unprecedented levels of aqueous swelling while maintaining a coherent multilamellar form. We found that combining cationic lipids with bicontinuous cubic phase-forming lipids (lipids with positive Gaussian modulus), results in the stabilization of multilamellar phases against repulsive steric forces that typically lead to bilayer delamination at high degrees of swelling. Using ultra-small-angle X-ray scattering alongside confocal laser scanning microscopy, we characterized various super-swelled states of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and glycerol monooleate (GMO) lipids, as well as other analogous systems, at varied concentration and molar ratios. Through these experiments we established swelling profiles of various binary lipid systems that were near-linear with decreasing lipid volume fraction, showing maximum swelling with periodicity well above 200 nanometers.

42 ENGINEERING↗
DOE OSTI2021

Randomized Algorithms for Scientific Computing (RASC)

Randomized algorithms have propelled advances in artificial intelligence (AI) and represent a foundational research area in advancing AI for Science. Future advancements in DOE Office of Science priority areas such as climate science, astrophysics, fusion, advanced materials, combustion, and quantum computing all require randomized algorithms for surmounting challenges of complexity, robustness, and scalability. Advances in data collection and numerical simulation have changed the dynamics of scientific research and motivate the need for randomized algorithms. For instance, advances in imaging technologies such as X-ray ptychography, electron microscopy, electron energy loss spectroscopy, or adaptive optics lattice light-sheet microscopy collect hyperspectral imaging and scattering data in terabytes, at breakneck speed enabled by state-of-the-art detectors. The data collection is exceptionally fast compared with its analysis. Likewise, advances in high-performance architectures have made exascale computing a reality and changed the economies of scientific computing in the process. Floating-point operations that create data are essentially free in comparison with data movement. Thus far, most approaches have focused on creating faster hardware. Ironically, this faster hardware has exacerbated the problem by making data still easier to create. Under such an onslaught, scientists often resort to heuristic deterministic sampling schemes (e.g., low-precision arithmetic, sampling every nth element) and sacrifice potentially valuable accuracy. Dramatically better results can be achieved via randomized algorithms, reducing the data size as much as or more than naive deterministic subsampling can achieve, while retaining the high accuracy of computing on the full data set. By randomized algorithms we mean those algorithms that employ some form of randomness in internal algorithmic decisions to accelerate time to solution, increase scalability, or improve reliability. Examples include matrix sketching for solving large-scale least-squares problems (see Figure 1) and stochastic gradient descent for training machine learning models. We are not recommending heuristic methods but rather randomized algorithms that have certificates of correctness and probabilistic guarantees of optimality and near-optimality. Such approaches can be useful beyond acceleration, for example, in understanding how to avoid measure zero worst-case scenarios that plague methods such as QR matrix factorization.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Effects of Supercritical CO2 on Matrix Permeability of Unconventional Formations

We studied the effects of supercritical carbon dioxide (scCO2) on the matrix permeability of reservoir rocks from the Eagle Ford, Utica, and Wolfcamp formations. We measured permeability using argon before exposure of the samples to scCO2 over time periods ranging from days to weeks. We measured permeability (and the change of permeability with confining pressure) when both argon and scCO2 were the pore fluids. In all three formations, we generally observe a negative correlation between initial permeability and carbonate content—the higher the carbonate content, the lower the initial permeability. In clay- and organic-rich samples, swelling of the matrix resulting from adsorption decreased the permeability by about 50% when the pore fluid was scCO2 although this permeability change is largely reversible. In carbonate-rich samples, dissolution of carbonate minerals by carbonic acid irreversibly increased matrix permeability, in some cases by more than one order of magnitude. This dissolution also increases the pressure dependence of permeability apparently due to enhanced mechanical compaction. Despite these trends, we observed no general correlation between mineralogy and the magnitude of the change in permeability with argon before and after exposure to scCO2. Flow of scCO2 through μm-scale cracks appears to play an important role in determining matrix permeability and the pressure dependence of permeability. Extended permeability measurements show that while adsorption is nearly instantaneous and reversible, dissolution is time-dependent, probably owing to reaction kinetics. Our results indicate that the composition and microstructure of matrix flow pathways control both the initial permeability and how permeability changes after interaction with scCO2. Electron microscopy images with Back-Scattered Electron (BSE) and Energy Dispersive Spectroscopy (EDS) revealed dissolution and etching of calcite minerals and precipitation of calcium sulfide resulting from exposure to scCO2.

58 GEOSCIENCES↗
DOE OSTI2020

Hybrid Unilamellar Vesicles of Phospholipids and Block Copolymers with Crystalline Domains

Phospholipid (PL) membranes are ubiquitous in nature and their phase behavior has been extensively studied. Lipids assemble in a variety of structures and external stimuli can activate a quick switch between them. Amphiphilic block copolymers (BCPs) can self-organize in analogous structures but are mechanically more robust and transformations are considerably slower. The combination of PL dynamical behavior with BCP chemical richness could lead to new materials for applications in bioinspired separation membranes and drug delivery. It is timely to underpin the phase behavior of these hybrid systems and a few recent studies have revealed that PL–BCP membranes display synergistic structural, phase-separation, and dynamical properties not seen in pure components. One example is phase-separation in the membrane plane, which seems to be strongly affected by the ability of the PL to form lamellar phases with ordered alkyl chains. In this paper we focus on a rather less explored design handle which is the crystalline properties of the BCP component. Using a combination of confocal laser scanning microscopy and X-ray scattering we show that hybrid membranes of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and methoxy-poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL) display BCP-rich and PL-rich domains when the BCP comprises crystalline moieties. The packing of the hydrophilic part of the BCP (PEG) favors mixing of DPPC at the molecular level or into nanoscale domains while semi-crystalline and hydrophobic PCL moieties bolster microscopic domain formation in the hybrid membrane plane

phase-separation↗
DOE OSTI2021

Review of Swift Heavy Ion Irradiation Effects in CeO2

Cerium dioxide (CeO2) exhibits complex behavior when irradiated with swift heavy ions. Modifications to this material originate from the production of atomic-scale defects, which accumulate and induce changes to the microstructure, chemistry, and material properties. As such, characterizing its radiation response requires a wide range of complementary characterization techniques to elucidate the defect formation and stability over multiple length scales, such as X-ray and neutron scattering, optical spectroscopy, and electron microscopy. In this article, recent experimental efforts are reviewed in order to holistically assess the current understanding and knowledge gaps regarding the underlying physical mechanisms that dictate the response of CeO2 and related materials to irradiation with swift heavy ions. The recent application of novel experimental techniques has provided additional insight into the structural and chemical behavior of irradiation-induced defects, from the local, atomic-scale arrangement to the long-range structure. However, future work must carefully account for the influence of experimental conditions, with respect to both sample properties (e.g., grain size and impurity content) and ion-beam parameters (e.g., ion mass and energy), to facilitate a more direct comparison of experimental results.

42 ENGINEERING↗
NASA NTRS1980

Carbon-fiber technology

The state of the art of PAN based carbon fiber manufacture and the science of fiber behavior is surveyed. A review is given of the stabilization by oxidation and the subsequent carbonization of fibers, of the apparent structure of fibers deduced from scanning electron microscopy, from X-ray scattering, and from similarities with soft carbons, and of the known relations between fiber properties and heat treatment temperature. A simplified model is invoked to explain the electrical properties of fibers and recent quantum chemical calculations on atomic clusters are used to elucidate some aspects of fiber conductivity. Some effects of intercalation and oxidative modification of finished fibers are summarized.

Hansen, C. F.↗
NASA NTRS1988

Optical monitoring of protein crystal growth

The possibility of using various optical techniques for detecting the onset of nucleation in protein crystal growth was investigated. Direct microscopy, general metrologic techniques, light scattering, ultraviolet absorption, and interferometry are addressed along with techniques for determining pH value. The necessity for collecting basic data on the optical properties of the growth solution as a prerequisite to the evaluation of monitoring techniques is pointed out.

Choudry, A.↗
NASA NTRS1999

Seeded Growth of Colloidal Silica Particles

The method of seeded growth was studied for producing mondisperse colloidal silica particles. It was shown that particle size as well as weight percent solids could be controlled by using this method. The particles were characterized by transmission electron microscopy (TEM) and quasielastic light scattering (QELS). The particles were found to have a bimodal size distribution when examined by TEM. The particle size as determined by QELS was found to be roughly 10-20% larger than the particle size as determined by TEM. Furthermore, the polydispersity (standard deviation/mean particle size) as determined by QELS was found to be significantly lower than the polydispersity as determined by TEM. This underscores the importance of using TEM as a characterization technique for determining particle monodispersity. It was also noted that there was an increase in particle roughness as the weight percent of the silica particles increased and a new nucleation of particles was observed as the weight percent approached 13%. A recipe for producing monodisperse silica particles in the 150 nm size range is presented.

Wurm, David B.↗
NASA NTRS2003

The Building Blocks of Materials: Gathering Knowledge at the Molecular Level

Two start-up positions were created within SD46 to pursue developments in the rapidly expanding areas of biomineralization and nano-technology. As envisioned by Dr. Sandor Lehoczy, the new laboratories to be developed must have the capacity to investigate not only processes associated with the self-assembly of molecules but also the examination of self-assembled structures. For these purposes, laboratories capable of performing the intended function, particularly light scattering spectroscopy and atomic force microscopy were created. What follows then are recent advances arising from the development of these new laboratories. With the implementation of the Atomic Force Microscopy Facility, examples of investigations that determine a correlation between the molecular structure of materials and their macroscopic physical properties are provided. In addition, examples of investigations with particular emphasis on the physical properties of protein crystals, at the molecular level, and subsequent macroscopic characteristics are as provided. Finally, progress in fabrication of technology at the nano-scale levels at the developmental stage is also presented.

Source record↗
NASA NTRS2015

A Combined Study Investigating the Insoluble and Soluble Organic Compounds in Category 3 Carbonaceous Itokawa Particles Recovered by the Hayabusa Mission

At the 3rd International Announcement of Opportunity (AO), we have been approved for five Category 3 carbonaceous Itokawa particles (RA-QD02-0012, RA-QD02-0078, RB-CV-0029, RB-CV-0080 and RB-QD04-0052) recovered by the first Hayabusa mission of JAXA. In this investigation, we aim to provide a comprehensive study to characterize and account for the presence of carbon-bearing phases as suggested by the initial Scanning Electron Microscopy (SEM) analysis carried out by JAXA at the curation facility, and to describe the mineralogical components of the particles. The insoluble organic content of Itokawa particle has been investigated with the use of micro-Raman spectroscopy by Kitajima and co-workers [1]. The Raman spectra of Itokawa particles show broad G- and D-bands typical of low temperature material which offers an interesting contrast to the high metamorphic grade (LL4-6) of the Itokawa parent body. Amino acid analysis has been conducted by Naraoka et al. [2] to study the soluble organic component of Itokawa particles, but since it was a preliminary study and thus did not have the opportunity to target on Category 3 carbonaceous particles, only terrestrial contaminants were identified. The investigation will be carried out in the following order prioritized according to the progressive damage the analytical techniques can induce: (1) micro-Raman spectrometry, (2) two-step laser mass spectrometry (micro-L2MS), (3) ultra-high performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry (LC-FD/ToF-MS), and optimally if we can recover the particles after wet chemistry analysis, we will mount the samples and perform (4) electron beam microscopy (SEM, electron back-scattered diffraction [EBSD]) and (5) carbon X-ray absorption near edge structure spectroscopy (C-XANES). We will begin the analytical procedures upon receiving the samples in September/October. This work will provide us with an understanding of the variety and origins of the carbon-bearing phases present in primitive solar system bodies from a direct sample-returned mission, which is less likely hampered by risks of terrestrial contamination as compared to meteorite finds and falls.

Chan, Q. H. S.↗