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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on BaCa(CO3)2 by Materials Project

BaCa(CO3)2 crystallizes in the trigonal P321 space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.82–2.89 Å. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.40–2.62 Å. There are three inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All C–O bond lengths are 1.30 Å. In the second C4+ site, C4+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All C–O bond lengths are 1.30 Å. In the third C4+ site, C4+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All C–O bond lengths are 1.30 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Ba2+, two equivalent Ca2+, and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCa(GaO2)4 by Materials Project

BaCa(GaO2)4 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.76–3.38 Å. Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (2.40 Å) and four longer (2.47 Å) Ca–O bond lengths. Ga3+ is bonded to four O2- atoms to form corner-sharing GaO4 tetrahedra. There is two shorter (1.86 Å) and two longer (1.87 Å) Ga–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+, one Ca2+, and two equivalent Ga3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ba2+ and two equivalent Ga3+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one Ca2+, and two equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCa(CO3)2 by Materials Project

BaCa(CO3)2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Ba2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.72–3.31 Å. Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.72 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.29 Å) and two longer (1.30 Å) C–O bond length. In the second C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.28 Å) and two longer (1.31 Å) C–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent Ba2+ and one C4+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two equivalent Ca2+, and one C4+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two equivalent Ca2+, and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCa(CO3)2 by Materials Project

BaCa(CO3)2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Ba2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.76–3.20 Å. Ca2+ is bonded to seven O2- atoms to form distorted edge-sharing CaO7 pentagonal bipyramids. There are a spread of Ca–O bond distances ranging from 2.34–2.55 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.28 Å) and two longer (1.31 Å) C–O bond length. In the second C4+ site, C4+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.29 Å) and two longer (1.30 Å) C–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two equivalent Ca2+, and one C4+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two equivalent Ca2+, and one C4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent Ba2+ and one C4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ca2+, and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCa(FeO2)4 by Materials Project

BaCaFe4O8 crystallizes in the trigonal P-31m space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share edges with six equivalent BaO12 cuboctahedra, edges with twelve equivalent FeO4 tetrahedra, and faces with two equivalent CaO6 octahedra. There are six shorter (3.00 Å) and six longer (3.19 Å) Ba–O bond lengths. Ca2+ is bonded to six equivalent O2- atoms to form CaO6 octahedra that share corners with twelve equivalent FeO4 tetrahedra and faces with two equivalent BaO12 cuboctahedra. All Ca–O bond lengths are 2.38 Å. Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three equivalent CaO6 octahedra, corners with four equivalent FeO4 tetrahedra, and edges with three equivalent BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 57°. There is one shorter (1.88 Å) and three longer (1.91 Å) Fe–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+, one Ca2+, and two equivalent Fe3+ atoms. In the second O2- site, O2- is bonded in a linear geometry to three equivalent Ba2+ and two equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCa by Materials Project

CaBa is Tetraauricupride structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Ba is bonded to four equivalent Ba and eight equivalent Ca atoms to form a mixture of distorted face, edge, and corner-sharing BaBa4Ca8 cuboctahedra. All Ba–Ba bond lengths are 4.36 Å. There are four shorter (4.10 Å) and four longer (4.21 Å) Ba–Ca bond lengths. Ca is bonded in a distorted body-centered cubic geometry to eight equivalent Ba atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The relationship between below average cognitive ability at age 5 years and the child’s experience of school at age 9

Background At age 5, while only embarking on their educational journey, substantial differences in children’s cognitive ability will already exist. The aim of this study was to examine the causal association between below average cognitive ability at age 5 years and child-reported experience of school and self-concept, and teacher-reported class engagement and emotional-behavioural function at age 9 years. Methods This longitudinal cohort study used data from 7,392 children in the Growing Up in Ireland Infant Cohort, who had completed the Picture Similarities and Naming Vocabulary subtests of the British Abilities Scales at age 5. Principal components analysis was used to produce a composite general cognitive ability score for each child. Children with a general cognitive ability score more than 1 standard deviation (SD) below the mean at age 5 were categorised as ‘Below Average Cognitive Ability’ (BACA), and those scoring above this as ‘Typical Cognitive Development’ (TCD). The outcomes of interest, measured at age 9, were child-reported experience of school, child’s self-concept, teacher-reported class engagement, and teacher-reported emotional behavioural function. Binary and multinomial logistic regression models were used to examine the association between BACA and these outcomes. Results Compared to those with TCD, those with BACA had significantly higher odds of never liking school [Adjusted odds ratio (AOR) 1.82, 95% CI 1.37–2.43, p < 0.001], of being picked on (AOR 1.27, 95% CI 1.09–1.48) and of picking on others (AOR 1.53, 95% CI 1.27–1.84). They had significantly higher odds of experiencing low self-concept (AOR 1.20, 95% CI 1.02–1.42) and emotional-behavioural difficulties (AOR 1.34, 95% CI 1.10–1.63, p = 0.003). Compared to those with TCD, children with BACA had significantly higher odds of hardly ever or never being interested, motivated and excited to learn (AOR 2.29, 95% CI 1.70–3.10). Conclusion Children with BACA at school-entry had significantly higher odds of reporting a negative school experience and low self-concept at age 9. They had significantly higher odds of having teacher-reported poor class engagement and problematic emotional-behavioural function at age 9. The findings of this study suggest BACA has a causal role in these adverse outcomes. Early childhood policy and intervention design should be cognisant of the important role of cognitive ability in school and childhood outcomes.

Bowe, Andrea K.↗
NASA NTRS1994

Wall pressure fluctuations in the reattachment region of a supersonic free shear layer

The primary aim of this research program was to investigate the mechanisms which cause the unsteady wall-pressure fluctuations in shock wave turbulent shear layer interactions. The secondary aim was to find means to reduce the magnitude of the fluctuating pressure loads by controlling the unsteady shock motion. The particular flow under study is the unsteady shock wave interaction formed in the reattachment zone of a separated supersonic flow. Similar flows are encountered in many practical situations, and they are associated with high levels of fluctuating wall pressure. The free shear layer is formed by the flow over a backward facing step, using an existing model, with the base pressure on the step adjusted so that there is no pressure discontinuity at the lip. The shear layer therefore develops in a zero pressure gradient. The primary advantage of this flow configuration is that the reattachment process can be studied in the absence of a separation shock. The mean flow data, and some preliminary hot-wire measurements of the mass-flux fluctuations were made by Baca and Settles, Baca, Williams and Bogdonoff, who showed that the shear layer became self-similar at about 17 delta(sub 0) downstream of the lip, and that it grew at a rate typical of the observed Mach number difference (about 1/3rd the incompressible growth rate). The turbulence measurements were later extended by Hayakawa, Smits and Bogdonoff under NASA Headquarters support.

Smits, Alexander J.↗
DOE OSTI2021

Be like Oppenheimer: Donate your weapons information for the next generation of LANL researchers

You can follow the Lab’s first physicists, J. Robert Oppenheimer, Richard Feynman, Hans Bethe, and so many others through the years, plus know your information is helping future researchers — just like our first scientists did for you. How? Donate your physical or digital classified weapons records to the Lab’s National Security Research Center (NSRC), said Riz Ali, NSRC Director. The NSRC houses 80 years’ worth of one-of-kind records, which total in the millions and include nearly every medium imaginable. It is the Laboratory’s largest collection of research materials and the largest classified library of any Department of Energy lab. It all started with Oppenheimer, our first Lab director, and his Technical Library that was established during the Manhattan Project, which was the U.S. government’s top-secret effort to create the first atomic bombs to help end World War II. “Few NSRC patrons are aware that most of its vital materials come from the Lab’s own workforce,” said Chris C’de Baca, the NSRC’s Group Leader. “A significant portion of our critical material — which today’s researchers access regularly — is a direct contribution from research scientists. If people don’t contribute, then we won’t have the information we need when people come to the NSRC for research.”

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2023

AlGaN High Electron Mobility Transistor for High-Temperature Logic

Here we report on AlGaN high electron mobility transistor (HEMT)-based logic development, using combined enhancement- and depletion-mode transistors to fabricate inverters with operation from room temperature up to 500°C. Our development approach included: (a) characterizing temperature-dependent carrier transport for different AlGaN HEMT heterostructures, (b) developing a suitable gate metal scheme for use in high temperatures, and (c) over-temperature testing of discrete devices and inverters. Hall mobility data (from 30°C to 500°C) revealed the reference GaN-channel HEMT experienced a 6.9x reduction in mobility, whereas the AlGaN channel HEMTs experienced about a 3.1x reduction. Furthermore, a greater aluminum contrast between the barrier and channel enabled higher carrier densities in the two-dimensional electron gas for all temperatures. The combination of reduced variation in mobility with temperature and high sheet carrier concentration showed that an Al-rich AlGaN-channel HEMT with a high barrier-to-channel aluminum contrast is the best option for an extreme temperature HEMT design. Three gate metal stacks were selected for low resistivity, high melting point, low thermal expansion coefficient, and high expected barrier height. The impact of thermal cycling was examined through electrical characterization of samples measured before and after rapid thermal anneal. The 200-nm tungsten gate metallization was the top performer with minimal reduction in drain current, a slightly positive threshold voltage shift, and about an order of magnitude advantage over the other gates in on-to-off current ratio. After incorporating the tungsten gate metal stack in device fabrication, characterization of transistors and inverters from room temperature up to 500°C was performed. The enhancement-mode (e-mode) devices’ resistance started increasing at about 200°C, resulting in drain current degradation. This phenomenon was not observed in depletion-mode (d-mode) devices but highlights a challenge for inverters in an e-mode driver and d-mode load configuration.

42 ENGINEERING↗
DOE OSTI2024

Volumetric Additive Manufacturing of Dicyclopentadiene by Solid‐State Photopolymerization

Polymerization in the solid state is generally infeasible due to restrictions on mobility. However, in this work, the solid-state photopolymerization of crystalline dicyclopentadiene is demonstrated via photoinitiated ring-opening metathesis polymerization. The source of mobility in the solid state is attributed to the plastic crystal nature of dicyclopentadiene, which yields local short-range mobility due to orientational degrees of freedom. Polymerization in the solid state enables photopatterning, volumetric additive manufacturing of free-standing structures, and fabrication with embedded components. Solid-state photopolymerization of dicyclopentadiene offers a new paradigm for advanced and freeform fabrication of high-performance thermosets.

additive manufacturing↗
DOE OSTI2022

Novel Segregated Solid Propulsion System with Separately Stored Fuel and Oxidizer

Abstract The development and experimentation of a solid propulsion concept consisting of separate hydrogen‐rich solid propellant and solid oxidizer grains is presented. This system consists of an extremely fuel‐rich solid propellant, which, once ignited, undergoes a self‐sustaining decomposition to release fuel‐rich product gases, which are particularly rich in hydrogen gas. These relatively high‐temperature gases subsequently react with a solid oxidizer grain stored downstream. Progress in high‐nitrogen materials has allowed for the synthesis of fuel‐rich compounds that can store significant amounts of hydrogen, with little or no bound oxygen. With these new developments in propellant chemistry, a unique segregated propulsion system has been developed, creating an all‐solid propulsion system that combusts analogously to a reverse hybrid rocket system. Because of the physical separation of fuel and oxidizer, a higher level of safety is achieved which concurrently allows for the utilization of higher energy ingredients without the penalty of higher sensitivity. Theoretical performance calculations and experimental data have shown the potential for this system to compete with existing composite rocket propellants while having significant benefits in terms of safety, toxicity, and mission space. This paper presents a detailed overview of the conception, development, and testing of this propulsion system.

42 ENGINEERING↗
DOE OSTI2020

Risk assessment and ventilation modeling for hydrogen releases in vehicle repair garages

The availability of repair garage infrastructure for hydrogen fuel cell vehicles is becoming increasingly important for future industry growth. Ventilation requirements for hydrogen fuel cell vehicles can affect both retrofitted and purpose-built repair garages and the costs associated with these requirements can be significant. A hazard and operability (HAZOP) study was performed to identify risk-significant scenarios related to light-duty hydrogen vehicles in a repair garage. Detailed simulations and modeling were performed using appropriate computational tools to estimate the location, behavior, and severity of hydrogen release based on key HAZOP scenarios. Here, this work compares current fire code requirements to an alternate ventilation strategy to further reduce potential hazardous conditions. Modeling shows that position, direction, and velocity of ventilation have a significant impact on the amount of instantaneous flammable mass in the domain.

08 HYDROGEN↗
DOE OSTI2023

Liquid hydrogen storage system for heavy duty trucks: Configuration, performance, cost, and safety

In this work, we investigate the potential of liquid hydrogen storage (LH 2 ) on-board Class-8 heavy duty trucks to resolve many of the range, weight, volume, refueling time and cost issues associated with 350 or 700-bar compressed H 2 storage in Type-3 or Type-4 composite tanks. We present and discuss conceptual storage system configurations capable of supplying H 2 to fuel cells at 5-bar with or without on-board LH 2 pumps. Structural aspects of storing LH 2 in double walled, vacuum insulated, and low-pressure Type-1 tanks are investigated. Structural materials and insulation methods are discussed for service at cryogenic temperatures and mitigation of heat leak to prevent LH 2 boiloff. Failure modes of the liner and shell are identified and analyzed using the regulatory codes and detailed finite element (FE) methods. The conceptual systems are subjected to a Failure modes and effects analysis (FMEA) and a safety, codes, and standards (SCS) review to rank failures and identify safety gaps. The results indicate that the conceptual systems can reach 19.6% usable gravimetric capacity, 40.9 g-H 2 /L usable volumetric capacity and $174-183/kg-H 2 cost (2016 USD) when manufactured 100,000 systems annually.

08 HYDROGEN↗
DOE OSTI2021

Durable and Highly Selective Ion Transport of a Sulfonated Diels Alder Poly(phenylene) for Vanadium Redox Flow Batteries

In order to improve the durability and ion selectivity of a hydrocarbon membrane for vanadium redox flow batteries (VRFBs) a polymer was rationally designed with an external hydrophobic shell and internal hydrophilic core. The polymer was designed to prevent hydrophilic polymer chain aggregation by functionalizing the external polymer shell with hydrophobic side chains and attaching acid moieties onto the polymer backbone. The hydrophobic shell is the result of pentafluorobenzoyl group functionalization on the pendent aryl rings in a Diels Alder poly(phenylene) backbone. The internal polymer chain contains sulfonic acid moieties to impart hydrophilic character. The physical and electrochemical characteristics of the membrane were systematically studied and compared with widely used Nafion-212. The synthesized membranes were found to be superior to Nafion-212 not only in terms of lower vanadium ion permeability (4.25 x 10 -8 vs. Nafion-212: 6.0 x 10 -6 cm 2 min -1 ) but also in higher VRFB performance (EE = 89% and vs. Nafion-212: 85.5% at 40 mA/cm 2 ). The membrane also showed over three times higher capacity retention than Nafion-212 (0.075 % vs. 0.25 % capacity loss per cycle respectively) and excellent ex situ and in situ chemical stability.

25 ENERGY STORAGE↗
DOE OSTI2021

Tunable Infrared Laser Absorption Spectroscopy of Aluminum Monoxide $A^2\Pi_i $–$X^2\Sigma^+$.

We report the details of an infrared, laser absorption diagnostic capable of quantifying aluminum monoxide temperature and column density at 100 kHz repetition rate. This novel technique employs a near infrared MEMS-VCSEL to measure rotationally resolved optical absorption spectra of aluminum monoxide $A^2\Pi_i$ - $X^2\Sigma^+$ from approximately 7400 –7900 cm -1 . Temperatures and column densities are extracted from model regressions to provide temporally resolved thermochemical information on aluminum oxidation reactions. The measurement capability is demonstrated by performing 100 kHz measurement in the plume of an exploding bridgewire with measured temperatures of 3450–3100 K and column densities of 1– 11 x 10 16 cm -2 . To the authors knowledge, this is the first use of the AlO $A^2\Pi_i$ - $X^2\Sigma^+$ transition to characterize aluminum combustion environments. Details regarding signal extraction and calibration of MEMS-VCSEL spectra are also included. Although unsuccessful, efforts to extract kinetic temperature and column density from simultaneously measured, atomic aluminum 2 P 3/2,1/2 - 2 S 1/2 transitions at 7618 cm -1 and 7602 cm -1 are also described.

47 OTHER INSTRUMENTATION↗