Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “structure formation”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Nanomorphology of eco-friendly colloidal inks, relating non-fullerene acceptor surface energy to structure formation

Nanoengineered, eco-friendly, solution-processable electroactive materials are in demand for the growing field of printed electronics, and these material requirements can be achieved by the development of waterborne colloidal dispersions. Functionality in these composite materials can be tuned by thermodynamically modifying the material nanomorphology, often by creation of kinetically stabilized aqueous nanoparticle dispersions. In this work we demonstrate that the internal structure of organic nanoparticles is controlled by the surface energy difference between the polymeric donor material and the non-fullerene acceptor (NFA) material. Nanoparticles of the following donor–acceptor combinations, suitable for printed organic photovoltaics, have been synthesized: TQ1:N2200, TQ1:PNDIT10, P3HT:N2200, P3HT:o-IDTBR and P3HT:eh-IDTBR. Advanced synchrotron-based X-ray spectroscopy and microscopy are used to correlate the formation of core–shell nanoparticle morphology to the material surface energy. We subsequently present a viable avenue for customizing the blended nanoparticle structure into (i) core–shell, (ii) molecularly intermixed, or (iii) inverted shell–core structures. Our results showed that TQ1:PNDIT10 and P3HT:o-IDTBR nanoparticles were comprised of a donor-rich shell and an NFA-rich core, however, interestingly we show a reversal to the inverse NFA shell/donor core structure for TQ1:N2200, P3HT:N2200 and P3HT:eh-IDTBR nanoparticles, driven by the low surface energy of N2200 (23.7 mJ m –2 ) and eh-IDTBR (18.3 mJ m –2 ). This article is the first report of a flipped nanoparticle core–shell morphology comprising an NFA-rich shell for the miniemulsion synthesis route. The composition of the shells and cores was able to be controlled by the differential mismatch in the surface energy of the donor and acceptor materials, with ΔG surface > 0, ΔG surface = 0, and ΔG surface < 0 for acceptor core–donor shell, molecularly intermixed, and acceptor shell–donor core, respectively. Accordingly, we introduce an entirely overlooked new figure of merit (FoM) for customizing nanoparticulate colloidal inks: tunable surface energy of non-fullerene-based semiconductors. Finally, the establishment of this FoM opens up electroactive material design to a wide range of functional printing applications with varying device and ink structure requirements, thereby reshaping the nanoengineering toolkit for waterborne colloidal dispersions and hence printed electronics.

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

Unfolding Structure Formation in the Dark Universe via Weak Gravitational Lensing: from Pixels to Cosmology in the Dark Energy Survey and Roman Space Telescope

Weak gravitational lensing (deflection of light from distant galaxies due to the gravitational potential of intervening mass) is one of the most exciting probes in cosmology as it is sensitive both to the growth of the large-scale structure and the expansion history of the Universe. We can measure the coherent distortion of galaxy shapes (which we call cosmic shear) and infer the matter distribution. With next-generation imaging surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (Rubin LSST) and the Nancy G. Roman Space Telescope (Roman), there is immense new promise in understanding the fundamental nature of dark matter and dark energy. With datasets from current experiments like the Dark Energy Survey (DES), we see apparent cosmological tensions between experiments that may either be real and indicate new physics or new systematics we do not yet understand. LSST and Roman will increase the number of galaxies we have observed by an order of magnitude, leading to improved constraints on our cosmological model by up to 300%. These experiments will have the potential to prove if these cosmological tensions are real. However, our control of systematic uncertainties must also improve by similar levels to achieve the promise of what these missions can deliver. To achieve these scientific outcomes, the challenges of determining galaxy shapes and redshifts and modeling the impact of astrophysical effects must be solved. My PhD has focused on enabling weak lensing science in DES and Roman. I co-led the shear analysis teams in DES to produce the largest weak lensing galaxy sample, as well as the final DES cosmological analysis of cosmic shear. For Roman, I have led two papers characterizing and mitigating shear-related systematics with image simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Chemo-Mechanically Driven In Situ Hierarchical Structure Formation in Mixed Conductors (Final Technical Report)

This document is the Final Technical Report for the Early Career project DE-SC0018963. Essential materials for energy technologies tend to exhibit “hierarchical” functions – they perform multiple, inter-related tasks at different locations, across disparate length and time scales. To best support this heterogeneous function, there is a fundamental need to understand and direct formation of corresponding tailored hierarchical architectures. In particular, a wide variety of applications, from energy conversion and storage to sensing and gas separation, rely on oxide mixed ionic and electronic conductors (MIECs). These critical ceramic materials catalyze reactions at their surfaces and selectively transport both ionic and electronic species in the bulk. Ideally, MIECs should adopt hierarchical structures with 1) high surface areas, 2) surface compositions exhibiting high catalytic activity, and 3) microstructural connectivity in the direction needed for fast mass and charge transport. In practice, however, MIECs.

08 HYDROGEN↗
DOE OSTI2023

Multiscale modeling for high burnup structure formation and associated pulverization

This report summarizes the lower length scale modeling work performed in the fiscal year 2023 under the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program to capture the microstrutural evolution and associated pulverization criteria in the high burnup regions. This year, the resolution mechanisms within the cluster dynamics code has been updated and it influence on the bubble growth in HBS regions at the mesoscale is studied. To improve the accuracy of phase-field models of fission gas bubble growth, a new Helmholtz free energy for high-density Xe gas is derived from a virial equation of state. Two previously used strategies for representing net vacancy production in phase-field models of fission gas bubble growth are compared with each other and with analytical models of bubble growth. The vacancy source only model is found to be more convenient to parameterize realistically compared with the vacancy source+sink model. Furthermore, the phase-field-fracture simulation have been performed using MD- informed failure stress values and realistic HBS structure obtained from the phase-field simulations. We also present the uncertainty bands on prediction of the critical stress to account for the effect of the lower length scale variabilities on the failure criteria at the mesoscale. It is observed that pulverization may occur in partially restructured regions with restructuring fraction as low as 17%. In light of this, an update to the BISON’s pulverization criteria is recommended.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Thermoplastic Elastomers and Their Physical Gels Electrospun into Tunable Microfibrous Nonwoven Mats: Structure Formation and Property Enhancement

Abstract Thermoplastic elastomers (TPEs) based on styrenic block copolymers constitute excellent examples of self‐networking macromolecules that are employed in a wide range of contemporary technologies as molded parts. In such applications, these TPEs exist as dense (nonporous) films or other shapes. Here, it is first demonstrated that a series of commercial TPEs possessing comparable compositions can be electrospun from solution to form microfibers that are arranged into nonwoven mats that are breathable. An important consideration for microfiber formation is the copolymer molecular weight, which regulates i) the viscosity of the parent solution prior to electrospinning, ii) the ability of these copolymers to self‐assemble during electrospinning, iii) the microfiber morphology, and iv) the mechanical properties of the resultant microfibers. The addition of a midblock‐selective aliphatic oil to these TPEs yields thermoplastic elastomer gels (TPEGs), wherein the copolymer morphology and mechanical properties become highly composition‐tunable. Electrospinning TPEGs from a binary oil+solvent solution introduces a micelle inversion mechanism that begins with an oil‐rich micellar core and ends with a styrene‐rich micellar core, required for network stabilization, as the solvent dries during microfiber solidification. This work has implications for the production of controllably low‐modulus microfibrous materials possessing modestly improved toughness but exceptional extensibility and enhanced optical transparency.

Shamsi, Mohammad↗
DOE OSTI2021

Mechanistic in situ insights into the formation, structural and catalytic aspects of the La 2 NiO 4 intermediate phase in the dry reforming of methane over Ni-based perovskite catalysts

In this work, we focus on the stability and bulk/surface structural properties of the Ruddlesden-Popper phase La 2 NiO 4 and their consequences for dry reforming of methane (DRM) activity. Fuelled by the appearance as a crucial intermediate during in situ decomposition of highly DRM-active LaNiO3 perovskite structures, we show that La 2 NiO 4 can be equally in situ decomposed into a Ni/La 2 O 3 phase offering CO 2 capture and release necessary for DRM activity, albeit at much higher temperatures compared to LaNiO 3 . Decomposition in hydrogen also leads to an active Ni/La 2 O 3 phase. In situ X-ray diffraction during DRM operation reveals considerable coking and encapsulation of exsolved Ni, yielding much smaller Ni crystallites compared to on LaNiO 3 , where coking is virtually absent. Additionally, generalizing the importance of intermediate Ruddlesden-Popper phases, the in situ decomposition of La-based perovskite structures yields several obstacles due to the high stability of both the parent perovskite and the Ruddlesden-Popper structures and the occurrence of parasitic structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Gravitational Waves from Rapid Structure Formation on Microscopic Scales before Matter-Radiation Equality

We propose a new scenario for the formation of asteroid-mass primordial black holes (PBHs). Our mechanism is based on the annihilation of the string-wall network associated with thebreaking of a U(1) global symmetry into a discrete ZN symmetry. If the potential hasmultiple local minima (N > 1) the network is stable, and the annihilation is guaranteed by a biasamong the different vacua. The collapse of the string-wall network is accompanied bycatastrogenesis, a large production of pseudo-Goldstone bosons (pGBs) — e.g. axions,ALPs, or majorons — gravitational waves, and PBHs. If pGBs rapidly decay into products thatthermalize, as predicted e.g. in the high-quality QCD axion and heavy majoron models, they do notcontribute to the dark matter population, but we show that PBHs can constitute 100% of the darkmatter. The gravitational wave background produced by catastrogenesis with heavy unstable axions,ALPs, or majorons could be visible in future interferometers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Unveiling the effect of Ni on the formation and structure of Earth’s inner core

Ni is the second most abundant element in the Earth’s core. Yet, its effects on the inner core’s structure and formation process are usually disregarded because of its electronic and size similarity with Fe. Using ab initio molecular dynamics simulations, we find that the bcc phase can spontaneously crystallize in liquid Ni at temperatures above Fe’s melting point at inner core pressures. The melting temperature of Ni is shown to be 700 to 800 K higher than that of Fe at 323 to 360 GPa. hcp, bcc, and liquid phase relations differ for Fe and Ni. Ni can be a bcc stabilizer for Fe at high temperatures and inner core pressures. A small amount of Ni can accelerate Fe’s crystallization at core pressures. These results suggest that Ni may substantially impact the structure and formation process of the solid inner core.

58 GEOSCIENCES↗
DOE OSTI2025

Hydrogen bonding to the formate ligand: Structural characterization of 2,2′:6′,2″-terpyridine zinc formate·H 2 O

Here, two polymorphs of the 2,2’:6’,2”-terpyridine zinc formate compound (terpy)Zn(O 2 CH) 2 •H 2 O have been structurally characterized by X-ray diffraction. In each case, the formate ligands coordinate via a K 1 -monodentate coordination mode and participate in hydrogen bonding interactions with water molecules. Despite this similarity, however, the polymorphs exhibit different hydrogen bonding motifs. Specifically, while one polymorph forms chains in which water molecules link adjacent (terpy)Zn(O 2 CH) 2 molecules, the other polymorph consists of discrete tetranuclear [(terpy)Zn(O 2 CH) 2 •H 2 O] 4 moieties.

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

Effect of Al on the formation and structure of alkali-silica reaction products

The use of Al-rich supplementary cementitious materials can effectively reduce the expansion of concrete caused by alkali-silica reaction (ASR). However, the role of Al in mitigating the formation and structure of ASR products is only poorly understood, since direct investigation of the reaction in the micro-scale veins of aggregates is difficult. Recent successful synthesis of ASR products provides a unique opportunity to directly assess the role of Al in ASR. In this study, the effect of Al on the formation and structure of ASR products synthesized at 40 and 80 °C is investigated. It is found that the presence of Al in concentration lower than 0.1 mM neither prevents ASR nor alters the structure of the crystalline ASR products formed at 40 °C. However, formation of the crystalline ASR product at 80 °C is lowered at higher Al content due to the formation of a zeolitic precursor.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Microgravity effects on nonequilibrium melt processing of neodymium titanate: thermophysical properties, atomic structure, glass formation and crystallization

The relationships between materials processing and structure can vary between terrestrial and reduced gravity environments. As one case study, we compare the nonequilibrium melt processing of a rare-earth titanate, nominally 83TiO 2 -17Nd 2 O 3 , and the structure of its glassy and crystalline products. Density and thermal expansion for the liquid, supercooled liquid, and glass are measured over 300–1850 °C using the Electrostatic Levitation Furnace (ELF) in microgravity, and two replicate density measurements were reproducible to within 0.4%. Cooling rates in ELF are 40–110 °C s -1 lower than those in a terrestrial aerodynamic levitator due to the absence of forced convection. X-ray/neutron total scattering and Raman spectroscopy indicate that glasses processed on Earth and in microgravity exhibit similar atomic structures, with only subtle differences that are consistent with compositional variations of ~2 mol. % Nd 2 O 3 . The glass atomic network contains a mixture of corner- and edge-sharing Ti-O polyhedra, and the fraction of edge-sharing arrangements decreases with increasing Nd 2 O 3 content. X-ray tomography and electron microscopy of crystalline products reveal substantial differences in microstructure, grain size, and crystalline phases, which arise from differences in the melt processes.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Neutrinos as Dark Matter

Active neutrinos in standard cosmology were ruled out as a dark matter candidate in the 1980's. The reason is twofold: they are too light to account for the observed energy density of dark matter in the Universe, and their relativistic nature would spoil structure formation. In this note we suggest that an enhanced density of cold Standard Model active neutrinos today could behave effectively as dark matter, avoiding constraints from recombination and structure formation. Such an enhancement could be produced, for instance, by late-time decays of a light scalar field that is not in thermal equilibrium with the plasma. This mechanism is testable through the detection of the Cosmic Neutrino Background (C$\nu$B), which could have an average cosmological energy density a factor of $\sim 100-200$ times larger than expected in $\Lambda$CDM. The postulated light neutrinophilic scalar field may be observable, with Yukawa couplings in the range $y \sim 5 \times 10^{-16}-10^{-12}$. A scenario preferred by structure formation constraints is that the scalar is a Majoron, and the neutrinos have an inverted mass hierarchy.

Cline, James M. [McGill U.] (ORCID:000000017437419↗