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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Effect of heavy ion irradiation dose rate and temperature on α' precipitation in high purity Fe-18%Cr alloy

Cr-rich alpha prime precipitates (CrRP) induce hardening and embrittlement of FeCr alloys, but the kinetics of CrRP formation due to particle irradiation are not well understood. In this study, Fe18wt.%Cr alloy in solid solution state and pre-aged to produce relatively coarse CrRP was irradiated with 8 MeV Fe ions. The irradiation conditions involved two midrange doses of 0.37 and 3.7 displacements per atom (dpa), a wide range of dose rates (10 -5 –10 -3 dpa/s) and temperatures (300–450 °C). The distributions of CrRP after irradiation were studied with atom probe tomography (APT). The critical irradiation conditions to suppress CrRP formation were identified as 300 °C and 10-3 dpa/s; CrRP formation occurred readily at lower dose rates or higher temperatures. From 0.37 to 3.7 dpa, CrRP were observed to slightly grow at 350 °C and strongly coarsen at 450 °C. Specimens with pre-existing CrRP evolved into a similar precipitate distribution as detected after ion irradiation on solution annealed specimens at 300–350 °C to 0.37 dpa, indicating that the precipitate microstructure approaches a quasi-equilibrium for doses <1 dpa. Limited shrinking of pre-existing CrRP was observed after irradiation at 450 °C to 0.37 dpa, indicating a higher recovery rate at this temperature. Additionally, the evolution of CrRP is quantitatively explained by employing corrections to the historic Nelson-Hudson-Mazey precipitate stability model, and a radiation modified precipitation mechanism is proposed to account for the competition between radiation enhanced diffusion and ballistic dissolution which results in the modifications on both size and solute concentration of CrRP.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electrosynthesis of high purity ethylene using high-index facet Cu 2 O nanocrystals electrocatalyst

Electrochemical CO 2 reduction reaction (eCO2RR) to multi-carbon (C 2+ ) products with copper-based catalysts is often limited by poor selectivity. This challenge arises from the concurrent formation of various intermediates, dictated by the atomic arrangement and electronic properties of surface atoms. In this study, we found that copper (I) oxide (Cu 2 O) nanocrystals with 50 facets (50F-NC), predominantly featuring (211) facets that offers high density of under-coordinated sites, demonstrate superior ethylene (C 2 H 4 ) selectivity of 92% ± 2 with an overall current density of 212 mA/cm 2 at -650 mV vs RHE. Furthermore, after one month of storage in a 1 M KOH electrolyte, this catalyst demonstrated a C 2 H 4 Faradaic efficiency of 87% highlighting its stabile structure under strong alkaline environments. Here, operando electrochemical Raman spectroscopy revealed enhanced CO* intermediate coverage on the 50F-NC catalyst, correlating with improved C-C coupling. SEM, TEM, and XPS analyses, along with DFT calculations, suggested that Cu sites on the (211) facet of 50F-NC and those at the Cu/Cu 2 O interface formed in-situ due to the surface reconstruction during the reaction, are likely active sites for effective C-C coupling and sustained high-rate C 2 H 4 production.

Cu nano particle↗
DOE OSTI2020

The effect of microstructure on the relationship between grain boundary sliding and slip transmission in high purity aluminum

The relationship between grain boundary sliding (GBS) and slip transmission is investigated experimentally at grain boundaries in 99.99% aluminum with a through-thickness, coarse grained microstructure deformed in tension at 190 °C. Using scanning electron microscope enabled digital image correlation (SEM-DIC) and electron backscatter diffraction (EBSD), high resolution strain fields and microstructural information were measured to examine the influence of microstructural neighborhoods on interactions between GBS and slip transmission and strain localization. Several distinct cases are presented that highlight important microstructural factors that govern deformation near grain boundaries. The findings include (1) direct transmission and GBS were anti-compatible and facilitated by opposing boundary types (low misorientation and high energy grain boundaries respectively); (2) increased GBS activity was correlated with decreased indirect transmission behavior; (3) GBS accommodation at triple junctions was enabled by intragranular plasticity; and (4) the local intragranular plastic strain discontinuity between grains determined the magnitude of GBS gradients. Finally, this work provides insight into the nature of these mechanisms and can be used to identify strain transfer criteria that can lead to improved GBS-sensitive crystal plasticity models.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Continuous recovery of high-purity Kraft lignin from black liquor via simultaneous, liquid-phase acidification and purification

Here, a key advantage of the Sequential Liquid-Lignin Recovery and Purification (SLRP) process for the recovery of lignin from Kraft black liquor is the precipitation of a solvated, “liquid-lignin” phase (vs. the typical solid) during the CO 2 acidification step. Here, we have discovered that this lignin can also be maintained in a solvated state during the H 2 SO 4 acidification step if aqueous acetic acid from the Aqueous Lignin Purification with Hot Agents (ALPHA) process is incorporated into the H 2 SO 4 solution. As the liquid-lignin is converted from its salt form at pH = 9.5 to its acid form at pH = 2.5, the lignin initially solvated with water becomes solvated and thus liquefied with the organic–water solution. Maintaining the lignin in a solvated liquid state has two advantages: (1) the entire SLRP + ALPHA process, from starting black liquor to final lignin product, can be operated continuously; and (2) mass transfer of metals impurities out of the liquid-lignin phase is significantly enhanced, resulting in both a cleaner Kraft lignin product (~2000 ppm Na and 0.5-1.0 % ash) and reduced water washing.

09 BIOMASS FUELS↗
DOE OSTI2022

Formation of carbon and oxygen rich surface layer on high purity magnesium by atmospheric carbon dioxide plasma

Carbon and oxygen-rich corrosion barrier layer formed on Mg by a simple and scalable CO 2 atmospheric plasma (CO 2 -AP) process. The reactive CO 2 -AP interacts with the Mg surface and forms a unique layered structure with the top MgCO 3 /MgO-intermixed particulates pillars and the bottom dense layer. The surface features were simultaneously formed on the nano-/micro-structured MgO layer by carbonate molecules, plasma-active CO 2 molecules, and/or other volatile organic compounds on the nano-/micro-structured MgO particle layer. The resulting surfaces after CO 2 -AP were either hydrophobic or hydrophilic and exhibited lower anodic current or high resistance for Mg corrosion. For the hydrophobic surfaces of CO 2 -AP treated Mg, molecular dynamic simulations were performed to understand the origin of hydrophobicity and identified that the amorphous carbon layers formed on the Mg surface are the source. The environmentally benign abundant-gas-based process enables the cost reduction associated with waste treatment, generation of by-product, and supply of raw material.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Clean quartz matters for cosmogenic nuclide analyses: An exploration of the importance of sample purity using the CRONUS-N reference material

We report reference materials are key for assessing inter-laboratory variability and measurement quality, and for placing analytical uncertainty bounds on sample analyses. Here, we investigate four years of data resulting from repeated processing of the CRONUS-N reference material for cosmogenic 10 Be and 26 Al analyses. At University of Vermont, we prepared a CRONUS-N aliquot with most of our sample batches from 2013 to 2017; these reference material samples were then distributed to four different accelerator mass spectrometry facilities, yielding 73 10 Be analyses and 58 26 Al analyses. We determine CRONUS-N 10 Be concentrations of (2.26 ± 0.14) x 10 5 atoms g -1 (n = 73, mean, 1 SD) and 26 Al concentrations of (1.00 ± 0.08) x 10 6 atoms g -1 (n = 58, mean, 1 SD). We find a reproducibility of 6.3% for 10 Be and 7.7% for 26 Al (relative standard deviations). We also document highly variable 27 Al and Mg concentrations and a 10 Be dispersion twice as large as the mean AMS analytic uncertainty. Analyses of the CRONUS-N material with and without density separation demonstrate that non-quartz minerals are present in the material and have a large impact on measured concentrations of 27 Al, 10 Be, and impurities; these non-quartz minerals represent only a very small portion of the total mass (0.6–0.8%) but have a disproportionally large effect on the resulting data. Our results highlight the importance of completely removing all non-quartz mineral phases from samples prior to Be/Al extraction for the determination of in situ cosmogenic 10 Be and 26 Al concentrations.

58 GEOSCIENCES↗