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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

High Chrome Refractory Characterization: Part I. Impact of Melt Reduction/Oxidation on the Corrosion Mechanism

High Cr 2 O 3 containing Monofrax ™ K‐3 is a robust refractory that is used in the fiberglass industry and used in radioactive waste glass melters worldwide. Monofrax ™ K‐3 is tolerant of transition metal oxides but contains highly reduced solid solutions of spinels, that is, (Mg,Fe 2+ )(Al,Cr) 2 O 3 . Conversely, many of the waste feeds being processed are highly oxidizing. The K‐3 refractory corrosion was tested in sealed crucibles starting with slurried melter feed instead of prereacted glass called for by ASTM C621. Testing the refractory coupon during the feed‐to‐glass conversion exposes the refractory to the oxidizing and reducing species being released during vitrification, for example, NO 3 − , NO 2 − , CO 2 , CO , O 2 . Corrosion rates measured in highly oxidizing (high nitrate) feeds were ~1.8–2.8 times higher than those determined using prereacted glass or reduced feeds. Confirmatory corrosion rates were measured on Monofrax ™ K‐3 coupons immersed in oxidizing feed in a 1/100th‐scale HLW pilot‐scale melter. Corrosion is heterogeneous or incongruent as Ni and Fe in the waste glass exchange with Mg and Al in the refractory. An insoluble NiFe 2 O 4 spinel corrosion product is formed that can build up a protective layer along the refractory walls or spall and settle to the melter floor depending on melt pool convection/agitation.

Jantzen, Carol M.↗
DOE OSTI2015

Properties of reactively sputtered oxygenated cadmium sulfide (CdS:O) and their impact on CdTe solar cell performance

Oxygenated cadmium sulfide (CdS:O) is commonly used as the n-type window layer in high-performance CdTe heterojunction solar cells. This layer is deposited by reactive sputtering, but the optimal amount of oxygen in the sputtering ambient is highly dependent on the specific system and process employed. In this work, the intrinsic properties of CdS:O were measured as a function of the oxygen content (0%–10%) in the sputtering ambient and correlated to device performance with the goal of better defining optimal CdS:O properties for CdTe solar cells. Optimal performance was found using CdS:O films that contained ∼40 at. % oxygen as measured by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy confirmed these results and showed that oxygen is incorporated primarily as oxygenated sulfur compounds (SO{sub x}). Device efficiency improved from 10.5% using CdS to >14% with CdS:O due largely to increases in short-circuit current density as well as a modest improvement in open-circuit voltage. The transparency of the CdS:O films was well correlated with observed improvements in blue quantum efficiency with increasing oxygen content. The optical bandgap of as-deposited CdS:O was identified as a simple metric for process optimization and transfer, with 2.8 eV being ideal for the device architecture employed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Analysis of the surface density and reactivity of perfluorophenylazide and the impact on ligand immobilization

Perfluorophenylazide (PFPA) chemistry is a novel method for tailoring the surface properties of solid surfaces and nanoparticles. It is general and versatile, and has proven to be an efficient way to immobilize graphene, proteins, carbohydrates, and synthetic polymers. The main thrust of this work is to provide a detailed investigation on the chemical composition and surface density of the PFPA tailored surface. Specifically, gold surfaces were treated with PFPA-derivatized (11-mercaptoundecyl)tetra(ethylene glycol) (PFPA-MUTEG) mixed with 2-[2-(2-mercaptoethoxy)ethoxy]ethanol (MDEG) at varying solution mole ratios. Complementary analytical techniques were employed to characterize the resulting films including Fourier transform infrared spectroscopy to detect fingerprints of the PFPA group, x-ray photoelectron spectroscopy and ellipsometry to study the homogeneity and uniformity of the films, and near edge x-ray absorption fine structures to study the electronic and chemical structure of the PFPA groups. Results from these studies show that the films prepared from 90:10 and 80:20 PFPA-MUTEG/MDEG mixed solutions exhibited the highest surface density of PFPA and the most homogeneous coverage on the surface. A functional assay using surface plasmon resonance with carbohydrates covalently immobilized onto the PFPA-modified surfaces showed the highest binding affinity for lectin on the PFPA-MUTEG/MDEG film prepared from a 90:10 solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Manufacturing Readiness and Cost Impacts for PEM Stack and Balance of Plant

The results of two Manufacturing Readiness Assessments of PEM fuel cell stacks and material handling equipment (MHE) and backup power (BUP) PEM fuel cell systems are given. Design modifications of fuel cell systems were made because the initial, 2008 designs did not fully meet the operational requirements of the markets. This situation indicates the 2008 risk elements were overstated.For 2010 BUP and MHE fuel cell systems, manufacturers had not reached the Low Rate Initial Production (LRIP) defined in the 2008 MRA Report at 1,000 units per year per manufacturer.For fuel cell stacks, LRIP was demonstrated by more than one manufacturer.The federal tax incentive program has compensated for the initial high cost of fuel cell systems.The Balance-of-Plant (BOP) has not evolved as rapidly as the PEM fuel cell stack manufacturing readiness.The BOP in 2014 is as costly as the fuel cell stack for MHE applications.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

An Analysis of the Impact of Particle Growth on Transport Losses in Polymer-Electrolyte Fuel Cells

Voltage cycling causes catalyst nanoparticles in polymer-electrolyte fuel cells to grow. The concomitant loss of interfacial area results in larger kinetic, transport, and possibly ohmic overpotentials. This paper uses recently published experimental data and mathematical models to investigate the evolutions of transport and ohmic resistances to platinum nanoparticles located on the surface and inside the micropores of carbon black supports. Resistance to oxygen transport rises as surface area declines primarily because the flux to each remaining larger platinum particle increases. The path lengths governing oxygen diffusion to surface and buried platinum sites also increase as nanoparticles grow. Platinum nanoparticles on the surface become relatively less favorable as voltage cycling proceeds because they grow faster than platinum in micropores. Because voltage cycling causes total interfacial area to decline, and the fraction located inside micropores to increase, nanoscale ohmic losses increase as a catalyst layer decays. The practical importance of this effect is difficult to discern because proton conductivity in carbon micropores is not well characterized.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2011

Indirect and semi-direct aerosol campaign: The impact of Arctic aerosols on clouds

A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the boundary layer in the vicinity of Barrow, Alaska, was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC). ISDAC's primary aim was to examine the effects of aerosols, including those generated by Asian wildfires, on clouds that contain both liquid and ice. ISDAC utilized the Atmospheric Radiation Measurement Pro- gram's permanent observational facilities at Barrow and specially deployed instruments measuring aerosol, ice fog, precipitation, and radiation. The National Research Council of Canada Convair-580 flew 27 sorties and collected data using an unprecedented 41 stateof- the-art cloud and aerosol instruments for more than 100 h on 12 different days. Aerosol compositions, including fresh and processed sea salt, biomassburning particles, organics, and sulfates mixed with organics, varied between flights. Observations in a dense arctic haze on 19 April and above, within, and below the single-layer stratocumulus on 8 and 26 April are enabling a process-oriented understanding of how aerosols affect arctic clouds. Inhomogeneities in reflectivity, a close coupling of upward and downward Doppler motion, and a nearly constant ice profile in the single-layer stratocumulus suggests that vertical mixing is responsible for its longevity observed during ISDAC. Data acquired in cirrus on flights between Barrow and Fairbanks, Alaska, are improving the understanding of the performance of cloud probes in ice. Furthermore, ISDAC data will improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales, and determine the extent to which surface measurements can provide retrievals of aerosols, clouds, precipitation, and radiative heating.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

The impacts of horizontal resolution on the seasonally-dependent biases of the northeastern Pacific ITCZ in coupled climate models.

Double-ITCZ has puzzled climate model community for more than two decades. Here, we found that over the eastern Pacific, precipitation and sea surface temperature (SST) biases in the NCAR CESM1 are seasonally-dependent, with positive (negative) precipitation/SST biases during boreal summer/fall (winter/spring), although the easterly wind bias persists around the year. This seasonally-dependent bias of precipitation/SST is found to be caused by the failure of the model to reproduce the climatological seasonal wind reversal of North American monsoon. During winter/spring, the climatological easterly wind dominates, so the stronger wind speed in the model enhances the evaporation and lowers the SST. It is opposite when the climatological wind turns to westerly during summer/fall. The easterly wind bias also occurs in the atmospheric model when the observation SST is prescribed, suggesting it is of atmospheric origin. Further, the easterly wind bias is mainly evident in the lower troposphere and quite independent of time, implying the effect of complex and narrow-ranged Central American topography, which is not depicted well in the coarse model resolution. When the model resolution is doubled, both SST and precipitation are improved with the reduced easterly wind bias. During boreal spring, when ITCZ bias is most significant, the northern and southern ITCZ can be improved by 29% and 18.8% respectively in the higher resolution. Finally, we suggest that these seasonally-dependent biases over the eastern Pacific are quite universal among 37 CMIP5 coupled models, and the ongoing CMIP6 project will provide a valuable opportunity to examine whether the bias can be reduced by increasing model resolution.

Song, Fengfei↗
DOE OSTI2020

On the Impact of Income, Age, and Travel Distance on the Value of Time

The value of time (VOT) is a fundamental component used in transportation modeling, policy analysis, and economic appraisal. Decades of research and practice have empirically estimated the VOT across many factors (e.g., mode, purpose, time, comfort, etc.), yet little is known about its underlying form. Although it is well established that VOT can vary, it is still unclear whether patterns exist in this variation. The objective of this paper is not to merely estimate the VOT, but to model the VOT across multiple continuous and interacting variables. The purpose is to reveal its functional form with respect to mode, age, gender, purpose, income, and time of day to provide a generalizable understanding for future research and practice. Such an understanding can help develop simpler models and reduce the need for bespoke estimations for every conceivable variable perturbation. This research utilized a household travel survey containing 14,159 reported trips with imputed travel time and costs for the alternative mode choices. The average overall estimated VOT is 40.32 $/h, with results showing VOT varying log-linearly with income and trip distance, but following a Gaussian function (normal curve) with age. Overall, the results show that travel distance dominates VOT variation, which increases exponentially at a rate that is 3.61 times higher per mile of distance than per $10,000 of income, and that VOT by age peaks at age 54. This basic understanding of how the VOT varies sets the foundation for answering the subsequent question for why it might vary.

Engineering↗
DOE OSTI2021

Impact of low reactivity fuel type on low load combustion, emissions, and cyclic variations of diesel-ignited dual fuel combustion

In this study, cyclic variations in dual fuel combustion with diesel ignition of three different low reactivity fuels (methane, propane, and gasoline) are examined under identical operating conditions. Experiments were performed on a single cylinder research engine (SCRE) at a low load of 3.3 bar brake mean effective pressure (BMEP). The start of injection (SOI) of diesel was varied from 280 to 330 absolute crank angle degrees (CAD). Engine speed, rail pressure, and boost pressure were held constant at 1500 rpm, 500 bar, and 1.5 bar, respectively. The energy substituted by the low reactivity fuel was fixed at 80% of the total energy input. It was found that diesel-methane (DM) and diesel-propane (DP) combustion were affected by diesel mixing to a greater extent than diesel-gasoline (DG) combustion due to the higher reactivity of gasoline. The magnitude of low temperature heat release was greatest for DG combustion followed by DM and DP combustion for all SOIs. The ignition delay for DG combustion was the shortest, followed by DM and DP combustion. DM and DP combustion exhibited more cyclic variations than DG combustion. Cyclic variations decreased for DM and DP combustion when SOI was advanced; however, DG combustion cyclic variations remained essentially constant for all SOIs. Earlier SOIs (280, 290, 300, and 310 CAD) for DM and (280, 290, and 300 CAD) for DP combustion indicated some prior-cycle effects on the combustion and IMEP (i.e. some level of determinism).

Engineering↗
DOE OSTI2022

Experimental study of the impact of scavenging efficiency on diesel combustion in an opposed-piston two-stroke engine

The opposed-piston two-stroke (OP2S) engine is a promising alternative powertrain technology that can offer thermal and brake efficiency improvements over conventional four-stroke engines. In recent years, many of the technical barriers of the OP2S engine architecture have been overcome. However, there is still a need for fundamental studies to provide insight into the scavenging and combustion processes of the OP2S engine to help design and operate the most efficient combustion systems using this engine architecture. This work aims to provide such insights by analyzing experimental data collected on a 3-cylinder, 4.9 L OP2S engine. Specifically, a scavenging efficiency sweep, an engine speed sweep with a constant scavenging efficiency, and an engine speed with a constant pressure differential across the engine were studied in detail. It was found that in diesel combustion, as the scavenging efficiency decreased, the increase in temperature of the hot, internal residuals resulted in a significant increase in heat transfer. Despite lowering pumping losses, this resulted in an overall decrease in brake efficiency. When the bulk thermodynamic conditions of two different scavenging efficiency cases (67% and 72%) were matched at port closing, the lower scavenging efficiency case still displayed a 0.7 percentage point penalty in net thermal efficiency and an increase in engine-out indicated specific emissions of NOx of 18% due to residual stratification in the cylinder. The results presented in this work show that the optimal breathing strategy in diesel combustion on an OP2S engine architecture is one that results in a slightly under-scavenged environment at port closing. However, the results did show potential system-level efficiency benefits of decreasing scavenging efficiency, meaning that alternative fuels and combustion strategies without the constraints of diesel combustion could achieve system-level efficiency gains by running significantly under-scavenged.

Engineering↗
DOE OSTI2026

Data for Immediate Impacts of Soybean Cover Crop on Bacterial Community Composition and Diversity in Soil Under Long-Term Saccharum Monoculture

Saccharum yield decline results from long-term monoculture practices. Changes in cropping management can improve soil health and productivity. Below-ground bacterial community diversity and composition across soybean (Glycine max (L.) Merr) cover crop, Saccharum monoculture (30+ year) and fallowed soil were determined. Near full length (~1,400 base pairs) of 16S rRNA gene sequences were extracted from the rhizospheres of sugarcane and soybean and fallowed soil were compared. Higher soil bacterial diversity was observed in the soybean cover crop than sugarcane monoculture across all measured indices (observed operationational taxonomic units, Chao1, Shannon, reciprocal Simpson and Jackknife). Acidocateria, Proteobacteria, Bacteroidetes and Planctomycetes were the most abundant bacterial phyla across the treatments. Indicator species analysis identified nine indicator phyla. Planctomycetes, Armatimonadetes and candidate phylum FBP were associated with soybean; Proteobacteria and Firmicutes were linked with sugarcane and Gemmatimonadetes, Nitrospirae, Rokubacteria and unclassified bacteria were associated with fallowed soil. Non-metric multidimensional scaling analysis showed distinct groupings of bacterial operational taxonomic units (97% identity) according to management system (soybean, sugarcane or fallow) indicating compositional differences among treatments. This is confirmed by the results of the multi-response permutation procedures (A = 0.541, p = 0.00045716). No correlation between soil parameters and bacterial community structure was observed according to Mantel test (r = 211865, p = 0.14). Use of soybean cover-crop fostered bacterial diversity and altered community structure. This indicates cover crops could have a restorative effect and potentially promote sustainability in long-term Saccharum production systems.

Field Data↗
DOE OSTI2026

Data for Impact of Vertical and Seasonal Variation in Leaf Traits on Simulating Soybean Canopy Photosynthesis via 1D and 3D Modeling

Accurate modeling of photosynthesis is crucial for predicting crop productivity and quantifying the carbon cycle in agroecosystems. Leaf traits are essential inputs for modeling canopy photosynthesis. Yet, many existing models still use fixed plant functional type (PTF)-based values to parameterize leaf traits under a big-leaf or two-big-leaf assumption, neglecting their vertical profiles and seasonal changes. This simplification may introduce significant uncertainties in estimating gross primary productivity (GPP). In this study, we simulated soybean GPP and tested the effects of vertical and seasonal variation in three key leaf photosynthetic traits: the maximum carboxylation rate at 25 °C (Vcmax25), leaf chlorophyll content (LCC), and leaf mass per area (LMA) in the 1D-SCOPE and 3D-Helios models. Weekly field measurements were conducted during the growing season of 2024 to support the simulation. We designed ten leaf trait parameterization schemes by incorporating different combinations of vertical profiles and seasonal changes, while assuming homogeneous canopy architecture in both models. Our results revealed that Vcmax25 vertical and seasonal variation had the strongest influence on simulated GPP in both 1D and 3D models, while LCC and LMA effects were minimal. Particularly, the scheme with an empirically parameterized Vcmax25 profile achieved comparable performance to the scheme with the measured Vcmax25 profile. Both 1D-SCOPE and 3D-Helios accurately modeled GPP (SCOPE: R2 = 0.87, Bias = 0.55 µmol m⁻² s⁻¹; Helios: R2 = 0.9, Bias = 0.22 µmol m⁻² s⁻¹) under the most complex scheme, and their responses to vertical and seasonal variation in leaf traits were consistent, demonstrating the robustness of our findings. Based on our findings, we propose a scalable framework for parameterizing leaf traits to improve GPP simulations. This study contributes to improving the representation of leaf trait dynamics in canopy-level photosynthesis models, potentially enhancing our ability to predict crop productivity and understand agroecosystem carbon dynamics.

Photosynthesis↗
DOE OSTI2026

Data for Impacts of Legacy and Contemporary Nitrogen Inputs on N2O and CO2 Emissions in Miscanthus and Maize Cultivated Soils

Nutrient inputs influence the sustainability of bioenergy crop production through contemporary (shortly after addition) and legacy effects (persisting over years) on microbial nitrogen (N) and carbon cycling, which contribute to greenhouse gas emissions. However, the relative importance of contemporary and legacy effects and how that could vary by crop functional types is poorly understood. Considering its rhizomatous roots and perennial growth, we hypothesized that Miscanthus × giganteu s ( M × g ) would be more sensitive to legacy N fertilization and the historical context of its environment than an annual crop like maize. To test this hypothesis, we examined the effects of legacy and contemporary N inputs on nitrous oxide (N2O) and carbon dioxide (CO2) emissions, as well as key N cycling genes in soils where M × g and maize were grown. A 150-day soil incubation experiment was conducted using soils from a long-term M × g and maize fertility experiment with three historic N fertilization rates (0, 112, and 336 kg N ha−1 year−1) and a contemporary amendment (60 mg N kg−1) with negative control (0 mg N kg−1). We observed significant increases in cumulative N2O emissions in M × g soils relative to maize soils, particularly at higher legacy fertilization rates, while contemporary N had no significant effect. Bacterial amoA gene abundance, which plays a significant role in nitrification in nutrient-rich soils, also increased with higher legacy fertilization rates in M × g soils but was unaffected by the contemporary N. In maize soils, legacy and contemporary N did not significantly affect N2O emissions, but cumulative CO2 emissions and amoA gene abundance significantly increased. The abundances of norB genes were not significantly influenced by either legacy fertilization or contemporary N amendments in either soil. Our findings demonstrate the greater importance of fertilization history over contemporary N in mediating soil N2O emissions, particularly for perennial bioenergy crops.

Carbon↗