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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

CO 2 –Brine Contact Angle Measurements on Navajo, Nugget, Bentheimer, Bandera Brown, Berea, and Mt. Simon Sandstones

In this study, contact angles were measured for CO 2 bubbles on six different sandstones (Navajo, Nugget, Bentheimer, Bandera Brown, Berea, and Mt. Simon) that could potentially represent properties of CO 2 storage depositional environments. The impacts of pressure and temperature were studied by focusing on the CO 2 phase behavior in three different scenarios: gaseous, liquid, and supercritical conditions. Despite controlling the sample preparation and cleanliness, CO 2 -brine equilibration conditions, and pressure and temperature, there were inconsistencies in contact angle trends that could largely be attributed to natural sample heterogeneity resulting from localized variations in topography, surface roughness, and mineral composition across the surface. Despite these variations, the analysis of 298 measurements from this study showed that 81% of the contact angles were below 40° representing strongly water-wet to (moderately) water-wet behaviors. Also, 17.3% of the measurements were between 40° and 60° (weakly water-wet) and primarily belonged to small CO 2 bubbles (< 500 μm) that were heavily impacted by localized surface heterogeneity in natural sandstone samples. Additionally, only 1.7% of the measurements had angles greater than 60° and could be classified as CO 2 -wet behavior, but these measurements occurred on extremely small bubbles (100-200 μm) that were very dependent on localized surface heterogeneity. While some of the detailed physics of the CO 2 -brine-sandstone interface is still poorly understood, from an application standpoint, the sandstones of this study were best characterized as strongly water-wet to (moderately) water-wet.

03 NATURAL GAS↗
DOE OSTI2020

Tutorial review on structure – dendrite growth relations in metal battery anode supports

This tutorial review explains the emerging understanding of the surface and bulk chemistry – electrochemical performance relations in anode supports (aka secondary current collectors, substrates, templates, hosts) for lithium, sodium and potassium metal batteries (LMBs, SMBs or NMBs, and KMBs or PMBs). In relation to each section, the possible future research directions that may yield both new insight and improved cycling behavior are explored. Representative case studies from Li, Na and K metal anode literature are discussed. The tutorial starts with an overview of the solid electrolyte interphase (SEI), covering both the “classic” understanding of the SEI structure and the “modern” insights obtained by site-specific cryogenic stage TEM analysis. Next, the multiple roles of supports in promoting cycling stability are detailed. Without an optimized support architecture, the metal–electrolyte interface becomes geometrically unstable at a lower current density and cycle number. Taking into consideration the available literature on LMBs, SMBs and KMBs, it is concluded that effective architectures are geometrically complex and electrochemically lithiophilic, sodiophilic or potassiophilic, so as to promote conformal electrochemical wetting of the metal during plating/stripping. One way that philicity is achieved is through support oxygen surface chemistry, which yields a reversibly reactive metal–support interface. Examples of this include the well-known oxygen–carbon moieties in reduced graphene oxide (rGO), as well as classic ion battery reversible conversion reaction oxides such as SnO 2 . Unreactive surfaces lead to dewetted island growth of the metal, which is a precursor to dendrites, and possibly to non-uniform dissolution. Surveying the literature on various Li, Na and K metal supports, it is concluded that the key bulk thermodynamic property that will predict electrochemical wetting behavior is the enthalpy of infinite solution (Δ sol H ∞ ) of the metal (solute) into the support (solvent). Large and negative Δ sol H ∞ promotes uniform metal wetting on the support surface, corresponding to relatively low plating overpotential. Positive Δ sol H ∞ promotes dewetted islands and a relatively high overpotential. This simple rule explains a broad range of studies on Li, Na and K metal – support interactions, including the previously reported correlation between mutual solubility and wetting.

25 ENERGY STORAGE↗
DOE OSTI2024

Scalable method of fabricating structured polymers for passive daytime radiative cooling and other applications

A switchable light transmission module is disclosed that includes a substrate having a first surface defining at least part of an enclosed volume, a porous layer disposed on the first surface and in fluid communication with the enclosed volume, and a reservoir in fluid communication with the enclosed volume. The reservoir is configured to supply a fluid to the sealed volume such that the fluid contacts the porous layer. The fluid has a refractive index that is close to the refractive index of the porous layer, has a high wettability for the porous layer, and does not dissolve the porous layer. When in a dry state, voids in the porous layer are filled with air which has a much different refractive index than the porous layer itself, resulting in a surface that is reflective and not very transmissive. During wetting of the porous layer by the fluid, however, those voids are filled with the fluid, reducing the difference in refractive index across the polymer-fluid interfaces such that light scattering is negligible and the surface becomes light permeable.

Mandal, Jyotirmoy↗
DOE OSTI2025

Designing slippery rough surfaces to enhance dropwise condensation of low surface tension fluid

Enhancing low surface tension liquid condensation is critical for achieving high energy efficiency and reducing the size of thermal energy systems. Extensive research has focused on promoting dropwise condensation of these liquids using state-of-the-art coatings on plain surfaces. However, maintaining dropwise condensation with low surface tension fluids is challenging due to rivulet formation, resulting in wetted tails that transition to filmwise condensation at elevated heat fluxes. Here, to address this issue, we uncover the role of surface structures and surface chemistry in the dropwise condensation of low surface tension ethanol on slippery rough surfaces (SRS). High-performance dropwise condensation has been achieved on slippery microchannels grafted with perfluoropolyether. The SRS uniquely facilitates rapid lateral droplet removal, enabling faster directional droplet shedding without rivulet formation. The resulting higher droplet removal frequency on SRS leads to heat transfer coefficients 100 % and 500 % higher than conventional dropwise and filmwise condensation on plain surfaces, respectively. Our findings uncover the pivotal role of rapid droplet removal through slippery microchannels in sustaining dropwise condensation of low surface tension liquids. This study introduces a new paradigm for promoting dropwise condensation using engineered SRS that incorporates surface structure and surface chemistry. The work will provide fundamental design guidelines to design efficient and compact condensers that use costly or flammable low global warming potential refrigerants in future refrigeration systems.

Dropwise condensation↗
DOE OSTI2024

Analysis of Dust and Corrosion Witness Samples Recovered from SNF Dry Storage Systems, Maine Yankee, 2023

This report documents the results of a long-term (5.79 year) exposure of 4-point bend corrosion test samples in the inlet and outlet vents of four spent nuclear fuel dry storage systems at the Maine Yankee Independent Spent Fuel Storage Installation. The goal of the test was to evaluate the corrosiveness of salt aerosols in a realistic near-marine environment, providing a data set for improved understanding of stress corrosion cracking of spent nuclear fuel dry storage canisters. Examination of the samples after extraction showed minor corrosion was present, mostly on rough-ground surfaces. However, dye penetrant testing showed that no SCC cracks were present. Dust collected on coupons co-located with the corrosion specimens was analyzed by scanning electron microscopy and leached to determine the soluble salts present. The dust was mostly organic material (pollen and stellate trichomes), with lesser detrital mineral grains. Salts present were a mix of sea-salts and continental salts, with chloride dominating the anions, but significant amounts of nitrate were also present. Both corrosion samples and dust samples showed evidence of wetting, indicating entry of water into the vents. The results of this field test suggest that the environment at Maine Yankee is not highly aggressive, although extrapolation from the periodically wetted vent samples to the hot, dry, canister surface may be difficult. No stress corrosion cracks were observed, but minor corrosion was present despite high nitrate concentrations in the salts. These observations may help address the ongoing question of the importance of nitrate in suppressing corrosion and SCC.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Gating of Hydrophobic Nanopores with Large Anions

In this report, understanding ion transport in nanoporous materials is critical to a wide variety of energy and environmental technologies, ranging from ion-selective membranes, drug delivery, and biosensing, to ion batteries and supercapacitors. While nanoscale transport is often described by continuum models that rely on a point charge description for ions and a homogeneous dielectric medium for the solvent, here, we show that transport of aqueous solutions at a hydrophobic interface can be highly dependent on the size and hydration strength of the solvated ions. Specifically, measurements of ion current through single silicon nitride nanopores that contain a hydrophobic-hydrophilic junction show that transport properties are dependent not only on applied voltage but also the type of anion. We find that in Cl - -contained solutions the nanopores only conducted ionic current above a negative voltage threshold. On the other hand, introduction of large polarizable anions, such as Br - and I - , facilitated the pore wetting, making the pore conductive at all examined voltages. Molecular dynamics simulations revealed that the large anions, Br - and I - , have a weaker solvation shell compared to that of Cl - , and consequently were prone to migrate from the aqueous solution to the hydrophobic surface, leading to the anion accumulation responsible for pore wetting. The results are essential for designing nanoporous systems that are selective to ions of the same charge, for realization of ion-induced wetting in hydrophobic pores, as well as for fundamental understanding on the role of ion hydration shell on the properties of solid/liquid interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Enable High-Energy LiNi0.5Co0.2Mn0.3O2 by Ultra-Thin Coating through Wet Impregnation

A high cut-off voltage is required for nickel-rich layered oxide LiNixCoyMnzO2 (NCM) to meet the high energy density requirement of lithium-ion batteries in electric vehicles. However, such a high voltage application leads to an unstable interface between NCM and liquid electrolytes. To stabilize the interface, the facile wet impregnation method has been developed to apply an ultra-thin Al2O3 coating layer on the NCM particles. This coating layer was found to have a strong interaction with the NCM and resulted in Al-doped NCM at the surface structure of NCM. The change of surface structure can not only reduce the surface resistance of lithium diffusion of LiNi0.5Co0.2Mn0.3O2 (NCM523), but also stabilize the solid electrolyte interface between NCM523 and the electrolyte with the cut-off voltage of 4.5 V vs. Li/Li+. Compared to other coating methods, wet impregnation coating can provide an ultra-thin and uniform coating with surface doping on NCM particles. Furthermore, this scalable coating method can be applied to various electrode materials without adding much additional cost.

25 ENERGY STORAGE↗
DOE OSTI2021

Evaluating Variable‐Resolution CESM Over China and Western United States for Use in Water‐Energy Nexus and Impacts Modeling

Abstract Climate models are critical tools to study earth system processes and are often further downscaled to provide refined‐resolution data sets for regional water‐energy impact analyses. In this study, the Variable‐Resolution Community Earth System Model (VR‐CESM), a new dynamical downscaling method, is employed to generate 1/8° simulations for China and the western United States over 1970–2006. Precipitation, temperature, snowpack, radiation, and wind speed are compared with two 1° global climate models, regional climate model ensemble, and reference data sets to evaluate their fidelity. Simulated precipitation skill is dependent upon the reference data sets used, a slight (<+10%) and spatially consistent wet bias in China during summer and the western United States during winter. Precipitation bias in VR‐CESM is the smallest among models and demonstrates the added value provided by resolution refinement. However, temperature biases are generally greater than precipitation due to more complicated interactions among processes. VR‐CESM simulates +2°C warm bias in the low‐elevation regions in China but −2°C cold bias in mountains. However, DJF cold bias (−2.23°C to−3.37°C) and JJA warm bias (+1.13°C to +1.87°C) exist in the western United States. The modeling skills of precipitation and temperature at various topographies are similar in the two evaluated regions. The cold bias was likely affected by downward shortwave radiation deficit (−15%) and slow bias of surface wind speeds (−16% to −29%). Despite the wet and cold bias, snow water equivalent and snow cover are underestimated in mountains. We conclude that VR‐CESM outperforms other models evaluated and provides the best estimation of downscaled climate model data for water‐energy studies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Modifying Surface Chemistry to Enhance the Electrochemical Stability of Nickel‐Rich Cathode Materials

Residual impurities such as lithium carbonate and hydroxide are a major concern for accelerating parasitic reactions at the cathode electrolyte interface of lithium-ion batteries. Removal of these lithium-bearing species becomes a necessity for high-performance nickel-rich cathode materials. Instead of directly removing these impurities through washing steps, a wet impregnation process is employed to convert these detrimental surface impurities into beneficial surface coating on nickel-rich cathode materials. Specifically, the pristine cathode material is treated with Al(H 2 PO 4 ) 3 solution to convert undesired compounds into Li 3 PO 4 and AlPO 4 , both of which are considered positive surface coating materials for high-voltage cathodes. It is found that the introduced modification greatly suppresses the interfacial impedance hike and improves the capacity retention of the cathode material after repeating charging/discharging. It is believed that these benefits are realized through the modification of the surface chemistry of the cathode material, which helps to slow down the parasitic reactions and reduce the damage to the cathode material.

25 ENERGY STORAGE↗
DOE OSTI2024

XPS analysis of molecular contamination and sp 2 amorphous carbon on oxidized (100) diamond

The efficacy of oxygen (O) surface terminations on diamond is an important factor for the performance and stability for diamond-based quantum sensors and electronics. Given the wide breadth of O-termination techniques, it can be difficult to discern which method would yield the highest and most consistent O coverage. Furthermore, the interpretation of surface characterization techniques is complicated by surface morphology and purity, which if not accounted for will yield inconsistent determination of the oxygen coverage. We present a comprehensive approach to consistently prepare and analyze oxygen termination of surfaces on (100) single-crystalline diamond. We report on x-ray photoelectron spectroscopy (XPS) characterization of diamond surfaces treated with six oxidation methods that include various wet chemical oxidation techniques, photochemical oxidation with UV illumination, and steam oxidation using atomic layer deposition (ALD). Our analysis entails a rigorous XPS peak-fitting procedure for measuring the functionalization of O-terminated diamond. The findings herein have provided molecular-level insights on oxidized surfaces in (100) diamond, including the demonstration of clear correlation between the measured oxygen atomic percentage and the presence of molecular contaminants containing nitrogen, silicon, and sulfur. We also provide a comparison of the sp 2 carbon content with the O1s atomic percentage and discern a correlation with the diamond samples treated with dry oxidation which eventually tapers off at a max O1s atomic percentage value of 7.09 ± 0.40%. Given these results, we conclude that the dry oxidation methods yield some of the highest oxygen amounts, with the ALD water vapor technique proving to be the cleanest technique out of all the oxidation methods explored in this work.

XPS↗
DOE OSTI2022

Understanding Platinum Ionomer Interface Properties of Polymer Electrolyte Fuel Cells

A well-designed cathode catalyst layer with optimal ionomer distribution is critical to minimizing amount of Platinum (Pt) content in polymer electrolyte fuel cells (PEFCs). The impact of Pt loading, ionomer content and carbon support types on the catalyst/ionomer interface were also investigated at dry and wet conditions. Higher Pt loadings resulted in higher double layer capacity (C dl ) and similar electrochemical surface area (ECSA) due to well dispersed ionic phase material. Higher ionomer content resulted in higher ionic conductivity but also showed similar SO 3 − group coverage. High surface area (HSA) carbon support had larger ECSA and C dl at both dry and wet conditions, as less agglomerated Pt was well dispersed in the meso-pores of the support. Lower SO 3 − group coverages were observed for HSA carbon than for Vulcan carbon due to Pt particles being buried within the porous HSA carbon support. The effect of cell conditioning and voltage recovery on the PEFC cathode catalyst layer was shown to have minimal impact on SO 3 − group coverage despite a decrease in C dl and ECSA due to the size increase of Pt particles. At dry condition, a significant increases in SO 3 − group coverage were observed for all MEAs due to higher adsorptivity of ionomer in dry conditions.

25 ENERGY STORAGE↗
DOE OSTI2022

Wickability-optimized textured liquid-desiccant air dehumidifiers for independent moisture management in energy-efficient buildings

Liquid-desiccant-based air conditioning systems are envisioned to enable independent humidity management, thereby improving the energy efficiency of future buildings. Existing liquid-desiccant-based air conditioning concepts, however, suffer from a poor liquid flow distribution deteriorating moisture removal rate. They are consequently flooded with the liquid-desiccant solution, which significantly degrades the energy efficiency of the dehumidification process. Here, in this work, the capillary forces and wickability effect of textured air dehumidifier surfaces are altered to minimize the liquid-desiccant flow rate of the fully wetted state, thereby transforming the physics of interfacial desiccant flow distribution. Consequently, the wickability-optimized air dehumidifier surface maximizes both moisture removal rate and dehumidification energy efficiency. It was interestingly found that the length scale of a textured air dehumidifier surface concept is optimized at an intermediate pattern density. Dry solid-air menisci appear at length scales exceeding the optimum pattern distance while the effective liquid–air interfacial area is reduced at smaller length scales, both of which degrade the moisture removal rate. At the optimum pattern density, the effective liquid–air interfacial area increases with the solution flow rate, thereby increasing the dehumidification rate. At a water vapor pressure potential of 3 kPa and a solution flow rate of 2.8 g/s, experimental results indicated a moisture removal rate of 0.16 g/m2-s for a textured surface concept with a capillary length scale of 3 mm, a 28% improvement compared with that of smooth-plate dehumidifier surfaces. A high moisture removal rate of the textured surface at a low desiccant flow rate led to a high thermal efficiency of 0.75 at a water vapor pressure potential of 5.6 kPa and a LiBr flow rate of 2.8 g/s. The insights gained from the present study accelerate the development of advanced textured surface concepts for next-generation liquid-desiccant-based air dehumidification systems offering independent humidity management for future energy-efficient buildings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Loss of energetic particles due to resistive wall mode instability in ITER

Effects of an unstable n = 1 (n is the toroidal mode number) resistive wall mode (RWM) on the energetic particle (EP) confinement and loss are numerically investigated, for an ITER steady state scenario with 10 MA plasma current and 5.3 T toroidal field. The eigenfunction of the RWM is computed, with the associated three-dimensional magnetic field perturbation superposed with the 2D equilibrium field for tracing the EP drift orbits. Considered are mono-energetic EPs at 0.5 MeV and 1 MeV for deuterium ions, and 3.5 MeV for fusion-born alphas, with a range of distribution in the particle pitch angle. Modeling finds that less than 20% of EPs can be lost to the limiting surface in ITER assuming a source distribution uniform in minor radius, due to an unstable RWM that produces 100 Gauss poloidal field perturbation at the outboard mid-plane just inside the (effective) resistive wall surface. On top of the initial prompt drift orbit loss for counter-current EPs, the RWM induced particle loss occurs on a one second time scale, which is comparable to the RWM growth time in ITER. The 'wetted' area, due to the lost EPs striking the limiting surface, is generally found to be large due to the RWM. This is a favorable prediction for ITER. Here, the loss distribution in the poloidal angle is more uniform for co-current EPs. Counter-current EPs experience outward orbit drift when launched from the low-field side, and tend to more often hit the bottom region of the limiting surface.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Surface functionality and formation mechanisms of carbon and graphene quantum dots

Graphene quantum dots (GQDs) and Carbon dots (C-dots) have been widely studied in recent years due to their structural and optoelectrical properties. These properties have prompted the exploration of the role of these carbon-based materials in many potential applications. This includes solar cells, photodetectors, bioimaging, sensors, batteries and drug delivery. These properties and applications of GQDs and C-dots are highly dependent on their size, shape and surface functionality. In this work, GQDs and C-dots mixtures have been synthesized by an inexpensive wet chemical method by varying the synthesis temperature from 85°, 100° to 115 °C. The surface functionalities of the synthesized carbon-based materials were investigated by several analytical methods. We discovered a higher degree of oxidation at higher temperatures. The mechanism of formation of different sized GQDs and C-dots with different functionalities have been explained with the help of XPS and NEXAFS analysis. The influence of size and surface functionalities on the optical properties of these nanomaterials is analyzed by UV–Vis and PL spectroscopic techniques. Furthermore, this study demonstrates that physicochemical properties of GQDs and C-dots can be controlled by changing the synthesis temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tailored Graphene Micropatterns by Wafer-Scale Direct Transfer for Flexible Chemical Sensor Platform

2D materials, such as graphene, exhibit great potential as functional materials for numerous novel applications due to their excellent properties. The grafting of conventional micropatterning techniques on new types of electronic devices is required to fully utilize the unique nature of graphene. However, the conventional lithography and polymer-supported transfer methods often induce the contamination and damage of the graphene surface due to polymer residues and harsh wet-transfer conditions. In this work, a novel strategy to obtain micropatterned graphene on polymer substrates using a direct curing process is demonstrated. Employing this method, entirely flexible, transparent, well-defined self-activated graphene sensor arrays, capable of gas discrimination without external heating, are fabricated on 4 in. wafer-scale substrates. Finite element method simulations show the potential of this patterning technique to maximize the performance of the sensor devices when the active channels of the 2D material are suspended and nanoscaled. This study contributes considerably to the development of flexible functional electronic devices based on 2D materials.

2D materials, Graphene, Microscale patterning, Che↗
DOE OSTI2022

Vapor Deposition Process for Engineering of Dispersed PEMFC ORR Pt/NbO x /C Catalysts

With support from the Department of Energy, and in partnership with Oak Ridge National Laboratory, Exothermics, Northeastern University, the University of Michigan, and IRD Fuel Cells, Ford has led an effort to use physical vapor deposition (PVD) to produce oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs). Conventional ORR catalysts are made by wet chemical processes, and experience loss of electrochemical surface area and activity over voltage cycling due to Pt dissolution and Pt particle coalescence. Not only was PVD processing researched as a means to reduce solvent waste and enhance reproducibility in catalyst manufacturing, but it was also perceived as a means to deposit preferential phases of niobium oxide onto the catalyst, which would then serve to prevent Pt particle movement and extend PEMFC lifetime.

08 HYDROGEN↗
DOE OSTI2023

Graphite-Salt Interactions: Summary of FY23 Activities

This report summarizes the research activities related to graphite–molten salt interactions during FY 2023. It includes results of FLiNaK infiltration experiments under various operating conditions, such as different temperatures, pressures, and times, to understand the effect of each condition on a variety of nuclear-grade graphites. Six graphite grades with various origins and properties were selected for the intrusion experiments using molten FLiNaK. The effect of intrusion pressure, temperature, and time were evaluated by measuring weight uptake, and the extent of penetration was studied using neutron tomography (n-CT). In addition, the wetting behavior of molten FLiNaK on a graphite surface was studied by measuring the contact angle on various grades of graphite. The results obtained by n-CT and contact angle measurements will help advance the understanding of factors that control the salt penetration in graphite and their relationship with intrinsic structural properties of the various graphite grades.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Climate Change Impacts on the South American Monsoon System and Its Surface–Atmosphere Processes Through RegCM4 CORDEX-CORE Projections

Here, we evaluate projected changes in surface water and energy balances and surface–atmosphere coupling in the South American Monsoon System (SAMS) for the end of the century (2080–2099). The analyses are based on two ensemble datasets, which follow Representative Concentration Pathway 8.5 in the future period, and cover four subdomains (Northern and Southern—NAMZ and SAMZ—Amazon, La Plata Basin—LPB, and Southern Southeast Brazil—SSB). One ensemble consists of three Global Climate Models (HadGEM2-ES, MPI-ESM-MR and NorESM1-M), while the other consists of their dynamically downscaled version at 25 km horizontal grid spacing using Regional Climate Model version 4 (RegCM4). As both ensembles are able in reproducing the annual cycle of the components of the surface water and energy balances in the present climate, they can be used in the study of future climate. During the wet season (November–March), both ensembles project a decrease in precipitation over NAMZ and SAMZ (an exception is RegCM4 that projects a slight increase in SAMZ), and an increase across the LPB and SSB. These changes do not cause retreat or expansion of the monsoon area over the continent, which is similar to the present climate (1995–2014). For the wet season, the ensembles are in line with the presence of a strong surface–atmosphere coupling in LPB and SSB, weak coupling in SAMZ and very weak coupling in NAMZ. For future climate, the coupling is even weaker in NAMZ, which may be a driver for the negative changes in precipitation. For the other subdomains, while the ensembles project similar signals of precipitation changes, they disagree with the surface-atmosphere coupling highlighting the uncertainties in future climate.

54 ENVIRONMENTAL SCIENCES↗