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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The substantial role of May soil temperature over Central Asia for summer surface air temperature variation and prediction over Northeastern China

The slowly varying soil temperature can exert local and nonlocal influences on regional climate system, and may thus provide a critical source of subseasonal-to-seasonal climate prediction. In this study, we identify that soil temperature in May over the key region of Central Asia (42 °N–50 °N, 62 °E–80 °E, KRCA) from Noah, Mosaic, CLM and ERA-interim datasets is closely linked to variations of the surface air temperature, daily maximum temperature and hot days over Northeastern China in summer (June-July-August), with correlation coefficients of regional average detrended time series ranging from 0.42 to 0.54, and all significant at the 99% confidence level for the period of 1979-2018. The possible physical mechanism behind the substantial downstream impacts of soil temperature over Central Asia are explored via diagnostical analysis combined with regional climate model experiments. Warmer soil temperature in May over the KRCA tends to cause positive anomalies of geopotential height in summer over Northeastern China through the Rossby wave propagation, and associated stronger subsidence warming, less cloud cover, more solar radiation reaching the surface, higher planetary boundary layer, and stronger thermal advection at 850 hPa, which provide favorable conditions for warmer surface air temperature particularly in the daytime as well as more hot days. Here this study further reveals that soil temperature over Central Asia in May makes important contribution to prediction of summer surface air temperature, daily maximum temperature and hot days over Northeastern China in terms of regional average time series and spatial patterns. Our findings highlight the previously-unknown substantial role of antecedent soil temperature condition over Central Asia for summer surface air temperature variation and prediction over Northeastern China.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Payload concepts for investigations of electrostatic dust motion on the lunar surface

Significant experimental and computational investigations have explored the feasibility of electrostatically-motivated dust motion on the lunar surface. The motion of lunar dust influences our understanding of the evolution of the surface and may also present a hazard to future exploration vehicles and astronauts. The possibility of a sustained exploration presence on the lunar surface opens the door to long-term experiments on the lunar surface, akin to the science facilities on the International Space Station. We have identified four measurements/observations that would significantly advance our understanding of dust-plasma interactions on the lunar surface. In this context, we provide conceptual designs for payloads to obtain these observations: a Langmuir probe, dust deposit witness plate, regolith charge measurement instrument, and cameras to look for evidence of horizon glow. These payloads could deploy independently and sequentially, or together as a suite. The proposed payloads would provide key observations that would inform future modeling efforts and direct future in situ experiments to understand the dust-plasma environment, both for planetary science and spacecraft design applications.

42 ENGINEERING↗
DOE OSTI2022

High-throughput surface characterization to identify porosity defects in additively manufactured 316L stainless steel

In the present study, a high throughput (HT) methodology is applied to rapidly assess the surface characteristics of 83 additively manufactured 316L stainless steel. The variation in surface roughness (S a ) showed a good correlation with a dimensionless number (π) and provided direct linkages to the internal porosity defects. Lack-of-fusion regime relates to high surface roughness (S a > 5 µm), low dimensionless number (π < 61), and the presence of cavities in between the melt pool tracks. Balling regime correlates to high surface roughness (S a > 5 µm), intermediate dimensionless number (61 < π < 146), and non-uniform melt pool track width. Keyhole regime shows low surface roughness (S a < 5 µm), high dimensionless number (π > 146), and a curved melt pool track. This approach accelerates the process parameter discovery and minimizes the porosity defects for the LPBF process. The impact of the defects on the as-processed tensile mechanical properties demonstrates that samples with porosity exhibit up to 10% less tensile strength and 30% less ductility than optimal samples.

316L stainless steel↗
DOE OSTI2021

Development of a cell surface display system in Chlamydomonas reinhardtii

Cell-surface display systems are biotechnological techniques used to express heterologous proteins on the cell surface. Their application depends directly on the cell system used, as well as on the anchoring point for the surface displayed protein. To meet most application demands an inexpensive, safe, and scalable production platform, that reduces the economic barriers for large scale use is needed. Toward this goal, we screened three possible cell surface anchoring points in the green algae Chlamydomonas by fusing mVenus to prospective anchors moieties. The vectors harboring mVenus:anchor were screened for mVenus fluorescence and tested for cellular localization by confocal laser scanning microscopy. This strategy allowed the identification of two functional anchors, one for the cytoplasmic membrane using the MAW8 GPI-anchor signal, and one for the cell wall using the GP1 protein. We also exploited GP1 chemical and biological traits to release the fused proteins efficiently during cell wall shedding. Our work provides a foundation for surface engineering of C reinhardtii supporting both cell biology studies and biotechnology applications.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Small molecule crystals with 1D water wires modulate electronic properties of surface water networks

This work evaluates the effect of water vapor pressure on the surface conductivity of a hydrated small molecule crystal under dry and wet conditions. The crystal contains a discrete metal complex with waters of hydration in structural positions and in 1D water wires. Under dry conditions, the surface of the hydrated crystal behaves as a near ideal capacitor. Under wet conditions, the waters of hydration serve as a template to assemble surface water networks by organization of water from the environment. The surface water provides pathways for charge transfer attributed to proton mobility that increases conductivity by > 3 orders in magnitude. Modulation between wet and dry conditions tunes the conductivity of the crystal surface via a two-step process, which has been evaluated kinetically as a function of the water vapor pressure.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Surface and subsurface characterization of laser-interference structured Ti6Al4V

Ti6Al4V specimens were exposed to high-energy laser pulses of 1.24 J/cm 2 fluences per pulse using a two-beam optical configuration to attain laser-interference. In addition to the formation of periodic surface textures by laser-interference, scanning electron microscope (SEM) images demonstrated several microstructural changes on the surface processed. Moreover, the surface and subsurface of Ti6Al4V specimens were characterized for the as-received and laser-interference processed conditions using x-ray photoelectron spectroscopy (XPS) and electron energy dispersive spectroscopy (EDS). The XPS data showed that this laser technique is effective at removal of surface contaminants for Ti6Al4V. The XPS analysis also revealed the formation of an oxy-nitride layer on the laser treated material. Finally, the microstructure analysis indicates that grain refinement, dendrite and twin structures were found near the surface due to laser processing.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Site-specific surface reactivity on MgO for atomic layer deposition via selective hydration

Atomic layer deposition (ALD) is a powerful technique for thin film synthesis, offering atomic-scale precision and conformality. While ALD of MgO has been widely studied for applications in energy storage and microelectronics, its potential as surface on which deposition may be selective and defects repaired remains underexplored. Here, we present a combined theoretical and experimental investigation of MgO surface hydration and its implications for targeted ALD growth using water and dimethyl aluminum isopropoxide (DMAI) as reactants. We perform density functional theory (DFT) calculations to examine molecular and dissociative H 2 O adsorption on MgO (100) terraces and step-edge sites, including pristine surfaces and those with Mg/O vacancies. Reaction Gibbs free energies are calculated under various conditions to quantify surface reactivity. Our findings reveal facet- and defect-dependent hydration behaviors that align with experimental ALD growth trends on MgO (100). This study provides a molecular-level understanding of MgO surface chemistry critical for optimizing ALD processes for thin film growth and defect repair.

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

Exploring the impact of surface topography on Rayleigh-Bénard dry convection in the Pi cloud chamber using OpenFOAM: In cylindrical and rectangular geometries

The Pi convection-cloud chamber can generate steady-state turbulence in both rectangular and cylindrical shapes via Rayleigh-Bénard convection (RBC) by maintaining warm bottom and cold top surfaces. Although most experiments in the Pi chamber were conducted in cylindrical shapes, all previous Pi chamber simulations were conducted in a rectangular shape due to the limitations of those models to discretize a cylindrical domain when using the finite difference method therein. Here, we use OpenFOAM, an open-source finite-volume-based Computational Fluid Dynamics (CFD) software package, to conduct Large-Eddy Simulation (LES) of dry RBC in the Pi chamber at high Rayleigh numbers (10 8 to 10 9 ). Results show that large-scale circulation (LSC) direction varies in the chamber with a constant side wall temperature. Imposing a slight temperature imbalance at the side wall ranging from 0.1 to 0.7 degrees can lock the LSC, aligning better with Pi chamber observations, particularly at higher Rayleigh numbers. In addition, we examine the impact of surface topography on LSC and heat transfer in RBC systems within cylindrical and rectangular shapes under varying conditions. Results show that roughing top/bottom surfaces by adding bars of a few tens millimeters height can strengthen thermal plumes and enhance temperature fluctuations in the chamber. Furthermore, we observe that different bar height configurations lead to notable changes in LSC orientation and thermal stratification, highlighting the complex interactions between surface features and convection patterns. This finding highlights how surface topography and chamber geometry affect Rayleigh-Bénard convection, improving understanding of turbulent heat transfer and atmospheric boundary-layer processes. Direct Numerical Simulations (DNS) are also conducted to validate LES results. In conclusion, while LES effectively captures qualitative behaviors seen in DNS, it tends to underestimate velocity variances near walls, illustrating a trade-off between computational efficiency and accuracy.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Indirect electrochemical method for high accuracy quantification of protein adsorption on gold surfaces

We demonstrate the use of copper underpotential deposition (UPD) for measurement of the electrochemically active surface area of a protein-modified gold electrode. The kinetics of adsorption and the subsequent structural rearrangement of β-casein, as a model protein, on the surface of a gold electrode have been followed over time. The protein-free surface area was determined by measuring the charge derived from UPD copper deposition on the non-blocked surface area at different stages of adsorption. The behaviour of β-casein adsorption as a function of surface roughness and the microstructure of the gold electrode, as well as the concentration of the protein solution, are studied using this method.

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

Dimensionality effects on multicomponent ionic transport and surface complexation in porous media

Coulombic interactions between charged species in pore water and at surface/solution interfaces are of pivotal importance for multicomponent reactive transport in porous media. In this study, we investigate the impact of domain dimensionality on electrostatically coupled dispersion and surface-solution reactions during transport of acidic plumes and major ions in porous media. Column and quasi two-dimensional flow-through experiments were performed, with identical silica porous media and under the same advection-dominated conditions. Equal mass fluxes of different electrolyte solutions (i.e., HCl - pH ~ 2.8, NaBr - 100 mM, HCl - pH ~ 2.8 plus NaBr - 100 mM) were continuously injected in the 1-D and 2-D experiments and breakthrough curves of pH and major ions were measured at the outlet of the domains. The presence of pronounced ionic strength gradients in the transverse direction in the 2-D setup caused distinct retardation and transport behaviors of protons and major ions which were not observed in the one-dimensional column experiments. Furthermore, in the cases of salt electrolytes injection, considerably enhanced release of H + (>61%) from the quartz surface was observed in the multidimensional system compared to the one-dimensional setup. Reactive transport modeling was performed to reproduce the experimental outcomes and to analyse the coupling between transport processes, based on the Nernst-Planck formulation of diffusive/dispersive fluxes and on surface complexation reactions at the solid-solution interface. Electrostatic interactions between Na + , B – , and H + , and deprotonation of the quartz surface upon the formation of sodium outer-sphere complexes, are the primary controllers of the spatial and temporal features displayed by the pH and major ions measurements. The reactive transport simulations allowed us to interpret the experimental observations, to visualize the distribution and spatio-temporal evolution of dissolved and solid species, to identify a spatially heterogeneous zonation of Coulombic interactions with distinct behavior at the fringe and core of the injected plumes in the multidimensional setup, and to quantify the different components of the Nerst-Planck fluxes of the charged solutes. This study demonstrates that the domain dimensionality directly affects electrostatic interactions between charged aqueous species in the pore water and surface complexation reactions at the solid-solution interface. The non-trivial effects of dimensionality on multicomponent ionic transport result in a significantly different behavior in 1-D and 2-D systems.

58 GEOSCIENCES↗
DOE OSTI2023

Mineral surface-catalyzed oxidation of Mn(II) by bromate: Implications for the occurrence of Mn oxides on Mars

The occurrence of manganese (Mn) oxides on Mars is believed to be an indicator of an O 2 -rich paleoenvironment of Mars because Mn oxides often form through the oxidation of Mn(II) by O 2 on the surface of Earth. An alternative formation pathway was recently proposed, in which Mn(II) is oxidized by bromate (BrO 3 - ), a common oxidant in contemporary Martian regolith. However, the oxidation of Mn(II) by bromate in solution is kinetically controlled and slow unless using very high concentrations (100 mM) of reactants that may be irrelevant to the conditions of Mars. We conducted laboratory simulations to determine whether iron (Fe) oxides (hematite and goethite) and a phyllosilicate (montmorillonite), abundant minerals on the surface of Mars, could catalyze the oxidation of Mn(II) by bromate. Hematite and goethite, but not montmorillonite, dramatically accelerated the oxidation with a low concentration (1 mM) of Mn(II) and bromate under various solution conditions. Further, the reaction system was autocatalytic with Fe oxides initiating the oxidation of Mn(II) at the early stage and the subsequent catalysis mainly provided by the Mn oxide products. In contrast to producing Mn(IV)O 2 only during the homogeneous oxidation of Mn(II) by bromate in solutions, the heterogeneous mineral-surface catalyzed oxidation resulted in a mixture of Mn(III)OOH and Mn(IV)O 2 phases. Mn(III)OOH was an intermediate product and can be further oxidized by bromate to Mn(IV)O 2 . The occurrence and accumulation of the intermediate product MnOOH can be attributed to its rapid formation due to surface-enhanced nucleation and growth on Fe oxide surfaces and to its higher resistance to oxidation by bromate than Mn(III) ions or clusters. Overall, mineralsurface catalyzed oxidation of Mn(II) by bromate is favorable from both thermodynamic and kinetic perspectives, and can be a major pathway for the occurrence of Mn oxides on Mars where microorganisms are lacking to catalyze the reaction. Our study further improves our understanding of the thermodynamic and kinetic controls on Mn(II) oxidation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Investigating relationship between surface topography and emissivity of metallic additively manufactured parts

Due to the direct relationship between thermal history and mechanical behavior, in situ thermal monitoring is key in gauging quality of parts produced with additive manufacturing (AM). Accurate monitoring of temperatures in an AM process requires knowledge of environment and object parameters including object emissivity. The emissivity is dependent on several variables, including: wavelength, material composition, temperature, and surface topography. Researchers have been concerned with the thermal emissivity dependence on temperature since large ranges are seen in metal powder bed processes, but there is also an extensive range of surfaces produced by AM. This work focused on discovering what roughness characteristics control thermal emissivity through investigation of prototypic 316 stainless steel AM samples produced with a range of build conditions on a laser powder bed fusion machine. Through experimental measurements of emissivity using hemispherical directional reflectance (HDR), guided by simulations using a finite-difference time-domain (FDTD) Maxwell solver, it was found that combinations of existing roughness parameters describing both height and slope of the surface correlate well with emissivity changes. Furthermore, these parameters work well due to their apt description of surface features encouraging internal reflection, which is the phenomenon that increases emissivity when a surface falls under the geometric optical region conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reaction paths of methane activation and oxidation of surface intermediates over NiO on Ceria-Zirconia catalysts studied by In-situ FTIR spectroscopy

Methane activation over NiO/Ce 0.82 Zr 0.18 O 2 catalysts synthesized by combustion synthesis is studied by in-situ IR spectroscopy and correlated to the properties and oxygen speciation of the catalyst. Through XRD, H 2 -TPR, and pyridine adsorption followed by FTIR spectroscopy, the reducibility and Lewis acidity of the catalysts are assessed. In-situ FTIR spectroscopy is used to monitor the methane activation on catalyst surfaces. Complex IR features of methane-derived surface species are observed and are attributed to the formation of surface alkyl/alkoxy, aldehyde, formate/carbonate, and aromatic species. A data analysis algorithm is developed to evaluate the evolution of different surface species over time. The formation of formate and carbonate species is driven by adsorbed surface oxygen, while less reactive oxygen species associated with NiO allow for the production of aromatics and alkoxy intermediates. Finally, by tuning the reducibility and Lewis acidity of the catalyst, the selectivity to alkoxy intermediates can be improved.

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

Effects of particle shape and surface roughness on van der Waals interactions and coupling to dynamics in nanocrystals

The van der Waals interaction between colloids and nanoparticles is one of the key components to understanding particle aggregation, attachment, and assembly. While the ubiquity of anisotropic particle shapes and surface roughness is well-recognized in nanocrystalline materials, the effect of both on van der Waals forces and torques has not been adequately investigated. Here, in this study, we develop a numerical scheme and determine the van der Waals forces and torques between cubic particles with multiple configurations and relative orientations. Our results show that the van der Waals torque due to anisotropic particle shapes is appreciable at nearly all configurations and mutual angles, outcompeting Brownian motion for various materials systems and conditions. The effect of surface roughness increases this shape effect, resulting in stronger van der Waals interactions ascribed to protrusions in the rough surfaces. Moreover, a scaling analysis indicates that the surface roughness alters the separation dependence of the van der Waals force and, more importantly, significantly influences the dynamics of two approaching particles. Our results clearly demonstrate that surface roughness and anisotropic shape play a crucial role in the energetics and kinetics of various particle-scale and emergent phenomena, such as crystal growth by oriented attachment, nanomaterials synthesis and assembly, mud flow rheology, as well as the deposition of natural nanocrystals within the subsurface.

Arbitrary configurations↗
DOE OSTI2020

A new soil mixing layer model for simulating conservative solute loss from initially saturated soil to surface runoff

Surface water pollution due to solute loss from soil to surface runoff is a serious threat to the environment, and it is of great significance to predict the solute loss. While soil mixing layer theory has been widely used to predict the solute loss, it has been observed that the conventional soil mixing layer models with constant mixing layer depth underestimate solute concentration in surface runoff, and thus underestimate the solute loss after surface runoff starts. This study introduced a new soil mixing layer model with a new concept that the mixing layer depth increases downward with time after surface runoff occurs. This new concept was implemented by adding a mixing front between the soil mixing layer and its underlying soil layer, which is conceptually similar to the wetting front of soil infiltration given by the Green-Ampt equation. This is equivalent to treating the soil mixing layer as a deforming control volume. A mechanistic explanation for the new model was presented. This study also developed a closed form solution of the new model. The new model was evaluated by simulating five laboratory experiments conducted by two groups of researchers. The first two experiments have ponding water, and consider different drainage and runoff conditions at both early and late runoff times. The other three experiments do not have ponding water, and consider different infiltration conditions at the bottom of soil boxes. Simulation results of the five experiments show that the new model resolves the underestimation problem of conventional soil mixing layer models. The new model is subject to a total of six limits such as that the new model only considers conservative solute. Three limits are related to the assumptions used to derive the closed form solution, and they may be alleviated in a future research as briefly discussed at the end of the paper.

54 ENVIRONMENTAL SCIENCES↗
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

Leak-tight crack repair for 304L stainless steel using friction surfacing

Here, friction surfacing (FS) was investigated as a method for sealing 50 μm wide thru-cracks in 3-mm-thick 304L stainless steel (304L) plate. Friction surfacing was performed using two sizes of 304L consumable rod, with diameters of 9.52 mm and 12.7 mm, on two substrate conditions (clean and oxidized). Friction surfacing was able to deposit a 600 μm thick coating and repair cracks to a depth of 100 μm - 200 μm below the original surface, when using the 12.7-mm-diameter consumable rod for both substrate conditions. Helium leak rates of 10 -10 atm-cc/s were achieved on crack repairs, designating them as leak-tight by the ANSI N14.5 standard. Optical and scanning electron microscopy were used to investigate the coating microstructure and bond interfaces. In this study, the 12.7-mm-diameter rod performed better with disruption of the oxide layer on the oxidized substrate and providing a more homogenous coating. Mechanical properties of the coated samples were evaluated by performing micro-indentation, tensile, bending, and adhesion testing. Higher hardness in the coatings was observed due to the fine equiaxed grains resulting from dynamic recrystallization. Complete consolidation of plastically deformed material on the substrate and a strong diffusion bond across the interface was observed. This was reflected in tensile and bending properties of the FS coatings being comparable to those of uncoated specimen. No delamination of the FS coating was observed during adhesion testing. The results demonstrate that friction surfacing is a viable option to seal cracks in stainless steels.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Efficient screening of rare large pit anomalies on polished surfaces using a minimalist sampling scheme

Lawrence Livermore National Laboratory (LLNL) has made significant strides in generating clean energy through its inertial confinement fusion (ICF) experiments. These experiments rely on high-density carbon (HDC) coated shells to encapsulate the fusion fuel. The success of these experiments is heavily dependent on the surface quality of these shells, as even minor imperfections, such as deep pits, can negatively impact fusion yield. Ensuring the required smoothness involves an extensive surface-finishing process that spans approximately 20 stages, making it both time-intensive and resource-demanding. A critical challenge in this process is the need for high-resolution scans to detect rare deep pits, which can be costly and impractical if performed on every shell. This highlights the necessity of developing more efficient scanning methods to optimize time and cost without compromising accuracy. To address these challenges, we introduce a novel approach that employs the multivariate Dvoretzky–Kiefer–Wolfowitz (DKW) inequality to provide a probabilistic upper bound on the error in estimating pit distribution characteristics via a Kernel Density Estimator (KDE). This error bound enables efficient and reliable estimation of pit distribution characteristics at a specified statistical confidence level using a minimal number of surface scans. The integrated DKW-KDE approach was validated through surface-finishing experiments across two batches of HDC-coated shells, demonstrating consistent and robust performance across multiple stages of the surface-finishing experiments. The validation studies suggest that the integrated DKW-KDE approach achieves comparable accuracy in estimating the risk of deleterious large pits with six scans, thus conserving time and resources. Further evaluations show that performance remains consistent across batches and over multiple polishing stages. In conclusion, based on these findings, one can leverage the minimal-scan insights to strategically improve the bottleneck inspection process, thus enhancing the productivity and quality of shell polishing and similar challenging manufacturing processes.

Inertial confinement fusion↗