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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Effect of substrate rotation on domain structure and magnetic relaxation in magnetic antidot lattice arrays

Microdimensional triangular magnetic antidot lattice arrays were prepared by varying the speed of substrate rotation. The pre-deposition patterning has been performed using photolithography technique followed by a post-deposition lift-off. Surface morphology taken by atomic force microscopy depicted that the growth mechanism of the grains changes from chain like formation to island structures due to the substrate rotation. Study of magnetization reversal via magneto optic Kerr effect based microscopy revealed reduction of uniaxial anisotropy and increase in domain size with substrate rotation. The relaxation measured under constant magnetic field becomes faster with rotation of the substrate during deposition. The nature of relaxation for the non-rotating sample can be described by a double exponential decay. However, the relaxation for the sample with substrate rotation is well described either by a double exponential or a Fatuzzo-Labrune like single exponential decay, which increases in applied field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Characterization of domain structure in one-dimensional SrRuO{sub 3} nanostructure using synchrotron x-ray microdiffraction

SrRuO{sub 3} (SRO) thin films with a geometric shape of one-dimensional stripes can be epitaxially grown on a SrTiO{sub 3} (STO) substrate. Conventional X-ray reciprocal space map (RSM) measurements revealed that the stripes consist of multiple crystallographic domains. We performed synchrotron X-ray microdiffraction measurements to determine whether the single stripe of the SRO has a single crystallographic domain or not. Spacing between stripes is ~200 nm that is comparable to a beam size available for the microdiffraction. The synchrotron X-ray microdiffraction experiment was performed at BL13XU, SPring-8. RSMs of asymmetric diffractions around STO 204 reflection were measured by a broad-beam (200 × 200 µm{sup 2}) and the sub-micro-beam (250(h) × 190(v) nm{sup 2}). Both SRO 260 and 620 are seen in the RSM measured by the broad-beam due to the crystallographic twinning. On the other hand, only SRO 620 is observed in the RSM measured by the sub-micro-beam. The result shows the domain length of the single stripe SRO thin film is longer than the vertical beam size of 190 nm.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO{sub 2}-based thin films

Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO{sub 1.5}-0.93HfO{sub 2} films grown by pulsed laser deposition was investigated. To achieve in-plane lattice matching, indium tin oxide (ITO) and yttria-stabilized zirconia (YSZ) were selected as underlying layers. We obtained (100)- and (001)/(010)-oriented films on ITO and YSZ, respectively. Ferroelastic domain formation was confirmed for both films by X-ray diffraction using the superlattice diffraction that appeared only for the orthorhombic symmetry. The formation of ferroelastic domains is believed to be induced by the tetragonal–orthorhombic phase transition upon cooling the films after deposition. The present results demonstrate that the orientation of HfO{sub 2}-based ferroelectric films can be controlled in the same manner as that of ferroelectric films composed of conventional perovskite-type material such as Pb(Zr, Ti)O{sub 3} and BiFeO{sub 3}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Surface topography and crystal and domain structures of films of ferroelectric copolymer of vinylidene difluoride and trifluoroethylene

The crystallization of a copolymer from a solution at room temperature is found to lead to the formation of a metastable structure, characterized by the coexistence of ferroelectric and paraelectric phases. The fraction of the latter decreases after annealing above the Curie point. Atomic force microscopy (AFM) has revealed a difference in the surface topographies between the films contacting with air and the films contacting with a glass substrate. The microstructure of copolymer chains has been investigated by {sup 19}F NMR spectroscopy. The chain fragments with “defect” attached monomeric units are ejected to the surface. The character of the ferroelectric domains formed during crystallization and their size distribution are analyzed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Determination of L-AP4-bound human mGlu8 receptor amino terminal domain structure and the molecular basis for L-AP4’s group III mGlu receptor functional potency and selectivity

Here, L-2-Amino-4-phosphonobutyric acid (L-AP4) is a known potent and selective agonist for the Group III mGlu receptors. However, it does not show any selectivity among the individual group III mGlu subtypes. In order to understand the molecular basis for this group selectivity, we solved the first human mGlu8 amino terminal domain (ATD) crystal structures in complex with L-glu and L-AP4. In comparison with other published L-glu-bound mGlu ATD structures, we have observed L-glu binds in a significantly different manner in mGlu1. Furthermore, these new structures provided evidence that both the electronic and steric nature of the distal phosphate of L-AP4 contribute to its exquisite Group III functional agonist potency and selectivity.

Schkeryantz, Jeffery M.↗
DOE OSTI2019

Modeling and simulation of Ultrasonic Guided Waves propagation in the fluid-structure domain by a monolithic approach

The present study introduces the coupled multiphysics model as part of the structural health monitoring (SHM) system. In particular, the Ultrasonic Guided Waves (UGWs) propagation is tracked in order to identify the damage to the structure. For this purpose, a multiphysics mathematical model is proposed. The model constitutes a monolithically coupled system of acoustic and elastic wave equations (WpFSI problem) where the wave signal displacement measurements are analyzed as the UGWs propagates in the solid, fluid and their interface. The ultimate goal of this paper is to explore and develop the efficient numerical solution of the WpFSI problem using the finite element method. A detailed description of the modeling framework and conditions that facilitate the coupling is provided. To couple the displacement-based acoustic wave equations for the isothermal fluid with elastic wave equations for the Saint Venant-Kirchhoff material model, the present study uses a monolithic solution algorithm. In particular, at each time step, wave equations are transformed to a fixed reference configuration via the arbitrary Lagrangian-Eulerian (ALE) mapping and automatically adopt the boundary conditions from the previous time step. The implementation is accomplished via the finite element library deal.II (Goll et al., 2017) based software toolbox DOpElib (Bangerth et al., 2007) which provides modularized higher level algorithms. Beyond SHM systems, the model is relevant for problems from biomechanics and biomedicine, vibromechanics, poroelasticity as well as subsurface and porous media flow. Here, the model developed here serves as a first step towards the on-line SHM system modeling, where structural dynamics are accounted for.

42 ENGINEERING↗
NASA NTRS1981

Grand unification and possible matter-antimatter domain structure in the universe

The theory and basic concepts for the development of a matter-antimatter domain cosmology are outlined within the framework of the grand unified gauge theory paradigm. It is shown how spontaneous CP symmetry breaking leads to such a domain sturcture in the universe. Astrophysical data such as the cosmic gamma-ray background spectrum, cosmic-ray p flux measurements, and galaxy clustering are found to favor this point of view. Future tests of this form of big-bang cosmology are suggested and discussed, including tests using deep underwater cosmic ray neutrino detectors.

Stecker, F. W.↗
DOE OSTI2017

Facilitation of Ferroelectric Switching via Mechanical Manipulation of Hierarchical Nanoscale Domain Structures

Heterogeneous ferroelastic transition that produces hierarchical 90° tetragonal nanodomains via mechanical loading and its effect on facilitating ferroelectric domain switching in relaxor-based ferroelectrics were explored. Combining in situ electron microscopy characterization and phase-field modeling, we reveal the nature of the transition process and discover that the transition lowers by 40% the electrical loading threshold needed for ferroelectric domain switching. Our results advance the fundamental understanding of ferroelectric domain switching behavior.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Conservation and divergence of C-terminal domain structure in the retinoblastoma protein family

The retinoblastoma protein (Rb) and the homologous pocket proteins p107 and p130 negatively regulate cell proliferation by binding and inhibiting members of the E2F transcription factor family. Here, the structural features that distinguish Rb from other pocket proteins have been unclear but are critical for understanding their functional diversity and determining why Rb has unique tumor suppressor activities. We describe here important differences in how the Rb and p107 C-terminal domains (CTDs) associate with the coiled-coil and marked-box domains (CMs) of E2Fs. We find that although CTD–CM binding is conserved across protein families, Rb and p107 CTDs show clear preferences for different E2Fs. A crystal structure of the p107 CTD bound to E2F5 and its dimer partner DP1 reveals the molecular basis for pocket protein–E2F binding specificity and how cyclin-dependent kinases differentially regulate pocket proteins through CTD phosphorylation. Our structural and biochemical data together with phylogenetic analyses of Rb and E2F proteins support the conclusion that Rb evolved specific structural motifs that confer its unique capacity to bind with high affinity those E2Fs that are the most potent activators of the cell cycle.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Mechanistic View of hnRNPA2 Low-Complexity Domain Structure, Interactions, and Phase Separation Altered by Mutation and Arginine Methylation

hnRNPA2, a component of RNA-processing membraneless organelles, forms inclusions when mutatedin a syndrome characterized by the degeneration of neurons (bearing features of amyotrophic lateral sclerosis [ALS] and frontotemporal dementia), muscle,and bone. In this work we provide a unified structural view of hnRNPA2 self-assembly, aggregation, and interaction and the distinct effects of small chemical changes—disease mutations and arginine methylation—on these assemblies. The hnRNPA2 low-complexity (LC) domain is compact and intrinsically disordered as a monomer, retaining predominant disorder in a liquid-liquid phase-separated form. Disease mutations D290V and P298L induce aggregation by enhancing and extending, respectively, the aggregation-prone region. Co-aggregating in disease inclusions, hnRNPA2 LC directly interacts with and induces phase separation of TDP-43. Conversely, arginine methylation reduces hnRNPA2 phase separation, disrupting arginine-mediated contacts. These results highlight the mechanistic role of specific LC domain interactions and modifications conserved across many hnRNP family members but altered by aggregation-causing pathological mutations.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Macroscopic Monochalcogenide van der Waals Ferroics: Growth, Domain Structures, and Curie Temperature

Two-dimensional and layered van der Waals materials promise to overcome the limitations of conventional ferroelectrics in terms of miniaturization and material integration, but synthesis has produced only small (up to few micrometer-sized) ferroic crystals. Here, we report the realization of in-plane ferroelectric few-layer crystals of the monochalcogenides tin(II) sulfide and selenide (SnS, SnSe) whose linear dimensions exceed the current state of the art by up to 1 order of magnitude. Such large crystals allow the investigation of ferroic domain patterns that are unaffected by edges and finite-size effects. Analysis of the abundant stripe domains by electron microscopy and nanobeam electron diffraction shows two distinct domain types: twin domains separated by positively charged walls with alternating head-to-head and tail-to-tail polarization as well as not previously observed purely rotational domains connected by neutral domain walls with head-to-tail dipoles. Access to large crystals allowed the determination of the Curie temperature of few-layer SnSe van der Waals ferroelectrics, and it enables the investigation of this class of ferroelectrics by widely available methods such as polarized optical microscopy. Furthermore, the combination with layer transfer protocols promises uniform materials for exploring fundamentals and for implementing devices for information processing and energy conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Predicting the preferred morphology of hexagonal boron nitride domain structure on nickel from ReaxFF-based molecular dynamics simulations

An understanding of the nucleation and growth of hexagonal boron nitride (hBN) on nickel substrates is essential to its development as a functional material. In particular, fundamental insights into the formation of the hexagonal lattices with alternating boron (B) and nitrogen (N) atoms could be exploited to control hBN lattice morphologies for targeted applications. Here, the preferred shapes and edge configurations of atomically smooth hBN on Ni(111) were investigated using molecular dynamics (MD) simulations, along with reactive force field (ReaxFF) developed to represent the Ni/B/N system and the lattice-building B–N bond formation. The obtained hBN lattices, from different B : N feed ratios, are able to confirm that hBN domain geometries can indeed be tuned by varying thermodynamic parameters (i.e., chemical potentials of N and B) – a finding that has only been predicted using quantum mechanical theories. Here, we also showed that the nitrogen fed to the system plays a more crucial role in dictating the size of hBN lattices. With an increase of the relative N content, the simulated hBN domain shapes also transition from equilateral triangles to hexagons, again, consistent with the anticipation based on Density Functional Theory (DFT) calculations. Hence, a plausible approach to acquire a desired hBN nanostructure depends on careful control over the synthesis conditions, which now can benefit from reliable molecular simulations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Ferroelastic domain structure and phase transition in single-crystalline [PbZn 1/3 Nb 2/3 O 3 ] 1-x [PbTiO 3 ] x observed via in situ x-ray microbeam

(1-x)Pb(Zn 1/3 Nb 2/3 )O 3 -xPbTiO 3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this study, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25°C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (T C ), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surface-screening mechanisms in ferroelectric thin films and their effect on polarization dynamics and domain structures

For over 70 years, ferroelectric materials have been one of the central research topics for condensed matter physics and material science, an interest driven both by fundamental science and applications. However, ferroelectric surfaces, the key component of ferroelectric films and nanostructures, still present a significant theoretical and even conceptual challenge. Indeed, stability of ferroelectric phase per se necessitates screening of polarization charge. At surfaces, this can lead to coupling between ferroelectric and semiconducting properties of material, or with surface (electro) chemistry, going well beyond classical models applicable for ferroelectric interfaces. In this paper, we summarize recent studies of surface-screening phenomena in ferroelectrics. We provide a brief overview of the historical understanding of the physics of ferroelectric surfaces, and existing theoretical models that both introduce screening mechanisms and explore the relationship between screening and relevant aspects of ferroelectric functionalities starting from phase stability itself. Given that the majority of ferroelectrics exist in multiple-domain states, we focus on local studies of screening phenomena using scanning probe microscopy techniques. We discuss recent studies of static and dynamic phenomena on ferroelectric surfaces, as well as phenomena observed under lateral transport, light, chemical, and pressure stimuli. Finally, we also note that the need for ionic screening renders polarization switching a coupled physical–electrochemical process and discuss the non-trivial phenomena such as chaotic behavior during domain switching that stem from this.

36 MATERIALS SCIENCE↗