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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Vapor Treatment and In-situ Recrystallization by Copper Chloride on Cu(In,Ga)Se 2 Thin Film

Deposition of CIGS semiconductor thin films was performed at low temperature and high rate by three-stage coevaporation process on molybdenum coated glass substrate. Here, a vapor treatment was done in between the second and third stage by flashing CuCl 2 for 5 mins at 400 °C. A large change in morphology and crystal structure was observed after the treatment. XRD and SEM showed that small grains transformed into large grains. A smoother Ga profile was observed by SIMS measurements for the treated films as compared to as-deposited films. Furthermore, the Na profile was also modified in the recrystallized samples, with a lower content after recrystallization.

14 SOLAR ENERGY↗
DOE OSTI2021

Growth of topological insulator Bi 2 Se 3 particles on GaAs via droplet epitaxy

The discovery of topological insulators (TIs) and their unique electronic properties has motivated research into a variety of applications, including quantum computing. It has been proposed that TI surface states will be energetically discretized in a quantum dot nanoparticle. These discretized states could then be used as basis states for a qubit that is more resistant to decoherence. In this work, prototypical TI Bi2Se3 nanoparticles are grown on GaAs (001) using the droplet epitaxy technique, and we demonstrate the control of nanoparticle height, area, and density by changing the duration of bismuth deposition and substrate temperature. Within the growth window studied, nanoparticles ranged from 5 to 15 nm in height with an 8–18 nm equivalent circular radius, and the density could be relatively well controlled by changing the substrate temperature and bismuth deposition time.

Materials Science↗
DOE OSTI2020

Paleotopography controls weathering of Cambrian-age profiles beneath the Great Unconformity, St. Francois Mountains, SE Missouri, U.S.A.

ABSTRACT Precambrian (1.4 to 1.5 Ga) granite and rhyolite in the St. Francois Mountains at the northeast corner of the Ozark Plateau in Missouri has been altered down to a depth up to 8 meters below the Great Unconformity (the contact between Paleozoic sedimentary rock and underlying Precambrian). Petrographic, geochemical, and mineralogic data indicate that at least two events generated this alteration: 1) surficial weathering due to subaerial exposure of the granite before Cambrian burial—this material is preserved as a paleosol; and 2) alteration due to reaction with basinal fluids channeled along the unconformity from nearby sedimentary basins long after burial by Paleozoic strata. To assess the variation between surficial weathering and basinal fluid alteration, we measured and sampled for petrologic, geochemical, and mineralogic data in the rock at and just below the Great Unconformity at three paleoelevations. Whole-rock geochemical oxide and X-ray diffraction data indicate that K-metasomatism and highly crystalline illite occurred in each profile. The K increase reflects crystallization of authigenic feldspar and illite from basinal fluids that were channeled along the Great Unconformity during younger Paleozoic fluid-flow events. Each profile also exhibits an upward increase in altered feldspar crystals and highly crystalline kaolinite, and an upward decrease in Ca and Na. Such changes reflect soil formation due to reaction with meteoric water before Cambrian burial, indicating that the altered granite was a paleosol before Paleozoic basinal fluid-flow events. Notably, the paleosol at the highest paleoelevation displays the least amount of paleoweathering and the paleosol at the lowest displays the greatest amount of paleoweathering. These results demonstrate that not only can characteristics of the paleosol just below the Great Unconformity be recognized in the St. Francois Mountains, despite subsequent alteration, but also it is possible to detect variations in soil thickness that were controlled by slope steepness and, therefore, water availability and/or soil creep or failure. This spatial relationship is compatible with studies of modern soils which indicate that soil character varies with position on a slope.

Geology↗
DOE OSTI2020

TRUST-EABM Sensors in Environments (SE) Report: Release FY20

The objective of the Delivery Environments (DE) Testbeds to Reduce Uncertainties in Simulations and Tests (TRUST) project is to support the efficient and responsive development of experimental, modeling, and simulation capabilities for future systems by developing representative testbeds that can be exercised more easily and efficiently than a WR like assembly for the purposes uncertainty quantification [1][2][3]. The testbeds are intended to be experimentally exercised in current and future relevant engineering environments with complementary modeling and simulation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

May 7, 2020 - Explosive Supercell Thunderstorm In The SE TX Panhandle

These lightning strikes can be more dangerous than “normal” lightning associated with a regular thunderstorm in that the “bolts from the blue” often occur well away from where the precipitation is occurring at the surface. “Bolts from the blue” occurred at a measured distance of 33 miles and an estimated 35 to 50 miles away from where the precipitation was occurring with this storm.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Production of High Specific Activity 72 Se/ 72 As, 117m Sn and 203 Pb for Research and Clinical Applications: Effective target design, recycling of target material and radioisotope separation

This grant involved four objectives for producing high specific activity radionuclides using reactor and accelerator technologies that would find use in medical, industrial and research applications. This grant continued a collaboration between the scientists at the University of Washington (UW), the University of Missouri (MU) and Brookhaven National Laboratory (BNL) and addresses the need for high specific activity radionuclides, both reactor- and accelerator-produced, and for the training and education of radiochemists in isotope production, separations and precursor syntheses. All three institutions were involved in the projects, but to different degrees. The chemistry graduate students (Ph.D. program at MU) may have participated in an internship at one of the other institutions for training and project translation/facilitation.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2025

Development of High-Quality, Very Large-Grained Cd(Se,Te) Thin Films for CdTe Solar Modules (Final Technical Report)

TCF-21-25048 is a one-year project to quantify the potential attributes of recent NREL inventions where CdTe devices with grain sizes exceeding 100's of microns in lateral dimension can be fabricated using a novel seeded-epitaxial process. A CdSe0.1Te0.9 film is evaporated on commercially available transparent conducting oxide (TCO) where the latter surface roughness (Ra) has been reduced to < 1-nm. After NREL's colossal grain growth (CGG) process, the grain size of this "seed" layer is increased to 100-1000 um. CdTe is then deposited epitaxially resulting in a large-grain CdTe device structure without use of CdCl2. As of this report, we have: Demonstrated the feasibility of using Tec-15 substrates after surface roughness (Ra) reduction (nexTC); Developed reproducible CGG processes for this commercially available substrate; Developed a close-spaced sublimation (CSS) process for CdTe epitaxy using these substrates; Demonstrated that large-grain CdTe films have less sub-band (band tail) absorption than conventional, small-grain CdTe; Demonstrated that large-grain CdTe films (no CdCl2) have carrier lifetimes up to 1.5 ns; Demonstrated that carrier lifetimes in epi-CdTe films (no CdCl2) have comparable lifetimes when compared to the best pX-CdTe films (FSLR) treated with CdCl2; Started making large-grain CdTe devices using CGG templates and epitaxially deposited CdTe.

14 SOLAR ENERGY↗
DOE OSTI2024

TRUST Sensors in Environments: Accelerometers (SE-A) Report, Release FY24

The objective of the Delivery Environments (DE) Testbeds to Reduce Uncertainty in Simulations and Tests (TRUST) project is to quantify and help increase confidence in specific areas of computational and experimental capabilities that are applicable to the development, on-target assessment, and qualification of current and future delivery environments. The TRUST project consists of five "low-complexity", single-feature testbeds used to conduct experiments with accompanying models and simulations. Each of the five single feature testbeds aims to isolate an engineering feature or behavior of interest, then work towards improving the fundamental engineering understanding of that feature. Additionally, the single feature testbeds are used to identify capability development needs that can help reduce model and experimental uncertainty.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

TRUST Sensors in Environments: Thermocouples (SE-TC) Report Release FY24

The objective of the Delivery Environments (DE) Testbeds to Reduce Uncertainty in Simulations and Tests (TRUST) project is to quantify and help increase confidence in specific areas of computational and experimental capabilities that are applicable to the development, on-target assessment, and qualification of current and future delivery environments. More complete quantification of confidence in experimental and computational capabilities and the sufficient increase of confidence in those capabilities is critical to improving weapons engineering design, qualification, and assessment efforts that are critical to the current and future stockpile. This work uses and provides feedback on analysis tools and experimental results databases for efficient and responsive engineering which are currently under development.

42 ENGINEERING↗
DOE OSTI2025

TRUST Sensors in Environments: Fiber Optic Displacement (SE-FOD)

The objective of the Delivery Environments (DE) Testbeds to Reduce Uncertainty in Simulations and Tests (TRUST) project is to quantify and help increase confidence in specific areas of computational and experimental capabilities that are applicable to the development, on-target assessment, and qualification of current and future delivery environments. More complete quantification of confidence in experimental and computational capabilities and the sufficient increase of confidence in those capabilities is critical to improving weapons engineering design, qualification, and assessment efforts that are critical to the current and future stockpile. Under the TRUST work package, engineers use and provide feedback on analysis tools and experimental results and create databases for efficient and responsive engineering which are currently under development.

42 ENGINEERING↗
DOE OSTI2025

TRUST Sensors in Environments: Accelerometers (SE-A) Report Release FY25

The objective of the Delivery Environments (DE) Testbeds to Reduce Uncertainty in Simulations and Tests (TRUST) project is to quantify and help increase confidence in specific areas of computa tional and experimental capabilities that are applicable to the development, on-target assessment, and qualification of current and future delivery environments. The TRUST project consists of five "low-complexity", single-feature testbeds used to conduct experiments with accompanying models and simulations. Each of the five single feature testbeds aims to isolate an engineering feature or behavior of interest, then work towards improving the fundamental engineering understanding of that feature. Additionally, the single feature testbeds are used to identify capability development needs that can help reduce model and experimental uncertainty.

42 ENGINEERING↗
DOE OSTI2025

TRUST Sensors in Environments: Thermocouples (SE-TC), Release FY25

The Delivery Environments Testbeds to Reduce Uncertainty in Simulations and Tests (TRUST) project is a broad project intended to analyze simplified problems experimentally and with modeling and simulation. The purpose of analyzing these simplified problems is to extend solution methods to more complex problems, as well as understand deficiencies and gaps in knowledge of methods currently used in more complex analyses. The TRUST project encompasses several smaller testbeds intended to isolate individual phenomena. The testbed under consideration in this report is the Sensors in Environments: Thermocouples testbed. In previous years, the purpose of this testbed was to quantify uncertainty of thermocouple sensors. To accomplish this, an aluminum plate was placed in a thermal chamber and subject to various types of thermal loading. Thermocouples were placed in various locations on the aluminum plate in various configurations (e.g., embedded in the plate, placed under Kapton tape), and an effort was made to quantify uncertainty in these measurements. Finite element simulations were performed to investigate how sensitive these measurements were to parameters such as the boundary conditions on the plate and material properties. However, a fundamental source of uncertainty in this analysis was the convective heat transfer from the plate. Convective heat transfer is a complex physical phenomenon comprised of a number of interacting sub-processes and is difficult to predict accurately a priori. As such, the main purpose of this testbed in FY25 was to better understand, both experimentally and numerically, the convective heat transfer from the plate. This is a highly applicable problem to several more complex problems, as convective heat transfer occurs in nearly all problems where a body is moving through air. Numerically, this required a two-step approach. First, the air flow in the thermal chamber was in vestigated using computational fluid dynamics. The commercial solver Fluent was used to perform these simulations. From these simulations, a heat transfer coefficient over the surface of the plate was calculated. This heat transfer was then used as boundary conditions for finite element heat transfer simulations within the plate, which were performed using Abaqus. Significant effort was devoted to automating the handoff between these two solvers. Experimentally, previous thermocouple results in the plate were used to validate the time-dependent thermal profiles produced from Abaqus. Further experimental efforts were performed both to help validate the Fluent simulations and to inform its boundary conditions. For example, hot-wire anemometers were used to measure the velocity in the chamber, which would be particularly useful in understanding the chamber inlet velocity. Thermocouple measurements were also taken in the chamber, instead of only on the plate, to serve as validation evidence for the Fluent simulations. Numerical results showed that the Fluent to Abaqus workflow matched previous plate thermocouple measurements well. This type of handoff is useful for more complex experiments, or those that are not able to be examined in as great of detail as this testbed, as it was performed without any experimental input. Experimental results, however, were more mixed. The anemometers proved unreliable, with inconsistent measurements across all anemometers, even at locations that were nearly identical. On the other hand, the thermocouples provided a relatively rich view of the temperature field in the chamber.

42 ENGINEERING↗
DOE OSTI2020

Measurement of shunt resistance and conduction band offset in Cu(In,Ga)Se 2 solar cells through joint analysis of temperature and intensity dependence of open-circuit voltage and photoluminescence

Joint analysis studies of open-circuit voltage and photoluminescence intensity (PL-I) are reported for CuIn 1-x GaxSe 2 (CIGSe) solar cells. A range of compositions are investigated, including constant x=0.35 and x=0.55 as well as a graded composition profile having a minimum of x=0.25. Both the open circuit voltage and PL-I are measured as functions of temperature and illumination intensity. With these two measurements, a full model-based fitting of the temperature and illumination dependence allows extraction of the effects of window layer band offset and shunt resistance, in addition to bulk and interface recombination parameters. Finally, to quantitatively analyze the two distinct measurements jointly, the absolute PL-I is measured to obtain quasi-Fermi-level splitting.

14 SOLAR ENERGY↗
DOE OSTI2022

Selenocyanate derived Se-incorporation into the nitrogenase Fe protein cluster

The nitrogenase Fe protein mediates ATP-dependent electron transfer to the nitrogenase MoFe protein during nitrogen fixation, in addition to catalyzing MoFe protein-independent substrate (CO 2 ) reduction and facilitating MoFe protein metallocluster biosynthesis. The precise role(s) of the Fe protein Fe 4 S 4 cluster in some of these processes remains ill-defined. Herein, we report crystallographic data demonstrating ATP-dependent chalcogenide exchange at the Fe 4 S 4 cluster of the nitrogenase Fe protein when potassium selenocyanate is used as the selenium source, an unexpected result as the Fe protein cluster is not traditionally perceived as a site of substrate binding within nitrogenase. The observed chalcogenide exchange illustrates that this Fe 4 S 4 cluster is capable of core substitution reactions under certain conditions, adding to the Fe protein’s repertoire of unique properties.

59 BASIC BIOLOGICAL SCIENCES↗