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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Rate Dependent Multi-Mechanism Discharge of Ag 0.50 VOP 4 ·1.8H 2 O: Insights from In Situ Energy Dispersive X-ray Diffraction

Ag 0.50 VOPO 4 ·1.8H 2 O (silver vanadium phosphate, SVOP) demonstrates a counterintuitive higher initial loaded voltage under higher discharge current. Energy dispersive X-ray diffraction (EDXRD) from synchrotron radiation was used to create tomographic profiles of cathodes at various depths of discharge for two discharge rates. SVOP displays two reduction mechanisms, reduction of a vanadium center accompanied by lithiation of the structure, or reduction-displacement of a silver cation to form silver metal. In-situ EDXRD provides the opportunity to observe spatially resolved changes to the parent SVOP crystal and formation of Ag 0 during reduction. At a C/170 discharge rate V 5+ reduction is the preferred initial reaction resulting in higher initial loaded voltage. At a discharge rate of C/400 reduction of Ag + with formation of conductive Ag 0 occurs earlier during discharge. Discharge rate also affects the spatial location of reduction products. The faster discharge rate initiates reduction close to the current collector with non-uniform distribution of silver metal resulting in isolated cathode areas. The slower rate develops a more homogenous distribution of reduced SVOP and silver metal. This study illuminates the roles of electronic and ionic conductivity limitations within a cathode at the mesoscale and how they impact the course of reduction processes and loaded voltage.

25 ENERGY STORAGE↗
DOE OSTI2016

Post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon lithography [A post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon polymerization]

Here, two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structures of neurexophilin–neurexin complexes reveal a regulatory mechanism of alternative splicing

Neurexins are presynaptic, cell-adhesion molecules that specify the functional properties of synapses via interactions with trans-synaptic ligands. Neurexins are extensively alternatively spliced at six canonical sites that regulate multifarious ligand interactions, but the structural mechanisms underlying alternative splicing-dependent neurexin regulation are largely unknown. Here, we determined high-resolution structures of the complex of neurexophilin-1 and the second laminin/neurexin/sex-hormone-binding globulin domain (LNS2) of neurexin-1 and examined how alternative splicing at splice site #2 (SS2) regulates the complex. Our data reveal a unique, extensive, neurexophilin–neurexin binding interface that extends the jelly-roll β-sandwich of LNS2 of neurexin-1 into neurexophilin-1. The SS2A insert of LNS2 augments this interface, increasing the binding affinity of LNS2 for neurexophilin-1. Taken together, our data reveal an unexpected architecture of neurexophilin–neurexin complexes that accounts for the modulation of binding by alternative splicing, which in turn regulates the competition of neurexophilin for neurexin binding with other ligands.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Analysis of Deformation and Fracture Mechanisms in the Harvested Low-Dose Baffle Former Bolt via Advanced Mechanical Tests

This report details the production of tensile specimens from in-service irradiated baffle former bolts (BFBs) and presents the results of a pilot in-situ SEM/EBSD test conducted at Oak Ridge National Laboratory’s Low Activation Materials Development and Analysis (LAMDA) facility. The SEM/EDS results confirmed that the material is AISI 316L steel, not AISI 347, and that no Nb addition was detected in several analyzed locations. EBSD analysis of the microstructure revealed in-grain misorientation gradients indicative of cold work, likely caused by material processing, and no retained ferrite was identified. During straining, dislocation channel formation was the primary deformation mechanism, with twinning also observed in favorably oriented grains at local strains as small as ~1.5%. No strain-induced phase instability was observed, likely due to the fact that the Ni and Cr content reached the upper limits for the 316L steel specification. Multiple microfracture events were observed during the tensile test. Fine strain-induced pores formed at the channel-grain boundary intersection points, while coarser microcracks were associated with non-metallic inclusions. Data analysis is ongoing, and additional tests are planned in the near future to provide more statistics and details.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Integrated carbon capture and conversion: A review on C 2+ product mechanisms and mechanism-guided strategies

The need to reduce atmospheric CO 2 concentrations necessitates CO 2 capture technologies for conversion into stable products or long-term storage. A single pot solution that simultaneously captures and converts CO 2 could minimize additional costs and energy demands associated with CO 2 transport, compression, and transient storage. While a variety of reduction products exist, currently, only conversion to C 2+ products including ethanol and ethylene are economically advantageous. Cu-based catalysts have the best-known performance for CO 2 electroreduction to C 2+ products. Metal Organic Frameworks (MOFs) are touted for their carbon capture capacity. Thus, integrated Cu-based MOFs could be an ideal candidate for the one-pot capture and conversion. In this paper, we review Cu-based MOFs and MOF derivatives that have been used to synthesize C 2+ products with the objective of understanding the mechanisms that enable synergistic capture and conversion. Furthermore, we discuss strategies based on the mechanistic insights that can be used to further enhance production. Finally, we discuss some of the challenges hindering widespread use of Cu-based MOFs and MOF derivatives along with possible solutions to overcome the challenges.

42 ENGINEERING↗
DOE OSTI2018

Formation mechanisms of boron oxide films fabricated by large-area electron beam-induced deposition of trimethyl borate [Formation Mechanisms of Boron Oxide Fillms Fabricated by Large Area Electron Beam-Induced Deposition of Trimethyl Borate]

Boron-containing materials are increasingly drawing interest for the use in electronics, optics, laser targets, neutron absorbers, and high-temperature and chemically resistant ceramics. In this article, the first investigation into the deposition of boron-based material via electron beam-induced deposition (EBID) is reported. Thin films were deposited using a novel, large-area EBID system that is shown to deposit material at rates comparable to conventional techniques such as laser-induced chemical vapor deposition. The deposition rate and stoichiometry of boron oxide fabricated by EBID using trimethyl borate (TMB) as precursor is found to be critically dependent on the substrate temperature. By comparing the deposition mechanisms of TMB to the conventional, alkoxide-based precursor tetraethyl orthosilicate it is revealed that ligand chemistry does not precisely predict the pathways leading to deposition of material via EBID. Lastly, the results demonstrate the first boron-containing material deposited by the EBID process and the potential for EBID as a scalable fabrication technique that could have a transformative effect on the athermal deposition of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Developing Methods to Assess Changes in Mechanical Properties of Shale Modified by Engineered Mineral Precipitation

Fractures in subsurface shale formations serve multiple purposes, for example, in the recovery of resources in hydraulic fracturing or as potential harmful leakage passages through caprocks that may contribute undesired fluids to the atmosphere or functional groundwater aquifers. A proposed method to seal or influence fracture properties is Ureolysis-Induced Calcium Carbonate Precipitation (UICP), a bio-mineralization technology driven by the enzymatic hydrolysis of urea, resulting in the formation of calcium carbonate. The resulting calcium carbonate can bridge the gaps in fractured shale and reduce fluid flow through fractures. This study represents the first step toward determining the influence of UICP treatment on shale material and its subsequent mechanical strength properties. The goal of this preliminary work is twofold: first, we aim to identify a method to test tensile strength along a core axis and second, we seek to assess the effect of temperature on the tensile strength of intact, unfractured shale cores (2.54 cm (1 in) diameter, 5.08 cm (2 in) long for comparison with future fractured and UICP-treated cores. A modified Brazilian indirect tensile strength test successfully measured splitting tensile strength of shale cores from Eagle Ford and Wolfcamp formations at room temperature and 60°C.

clastic rock↗
NASA NTRS1972

Thermal and mechanical treatments for nickel and some nickel-base alloys: Effects on mechanical properties

This report deals with heat treating and working nickel and nickel-base alloys, and with the effects of these operations on the mechanical properties of the materials. The subjects covered are annealing, solution treating, stress relieving, stress equalizing, age hardening, hot working, cold working, combinations of working and heat treating (often referred to as thermomechanical treating), and properties of the materials at various temperatures. The equipment and procedures used in working the materials are discussed, along with the common problems that may be encountered and the precautions and corrective measures that are available.

Hall, A. M.↗
NASA NTRS1973

The orbital mechanics of flight mechanics

A reference handbook on modern dynamic orbit theory is presented. Starting from the most basic inverse-square law, the law of gravity for a sphere is developed, and the motion of point masses under the influence of a sphere is considered. The reentry theory and the orbital theory are discussed along with the relative motion between two bodies in orbit about the same planet. Relative-motion equations, rectangular coordinates, and the mechanics of simple rigid bodies under the influence of a gravity gradient field are also discussed.

Dunning, R. S.↗
NASA NTRS1986

Toughening mechanisms in elastomer-modified epoxies. I - Mechanical studies. II - Microscopy studies

Tensile dilatometry at constant displacement rates is presently used to ascertain whether voiding, crazing or shear banding are the deformation mechanisms at work in the toughening of brittle epoxies through the addition of an elastomeric phase. The results obtained for epoxies toughened by various levels of several types of carbonyl-terminated butadiene nitrile liquid rubber indicate that, at low strain rates, the rubber particles simply enhance shear deformation; at sufficiently high strain rates, the particles cavitate and promote further shear deformation. Examinations of these materials are conducted by means of SEM, TEM, and optical microscopy in the second part of this study. Toughening is hypothesized to involve cavitation's relieving of triaxial tension at the crack tip, as well as shear band formation, which creates a plastic zone.

Yee, A. F.↗
NASA NTRS1955

From linear mechanics to nonlinear mechanics

Consideration is given to the techniques used in telecommunication where a nonlinear system (the modulator) results in a linear transposition of a signal. It is then shown that a similar method permits linearization of electromechanical devices or nonlinear mechanical devices. A sweep function plays the same role as the carrier wave in radio-electricity. The linearizations of certain nonlinear functionals are presented.

RESEARCH TECHNIQUE, MATHEMATICS↗