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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Ultra-low radioactivity Kapton and copper-Kapton laminates

Polyimide-based materials, like Kapton, are widely used in flexible cables and circuitry due to their unique electrical and mechanical characteristics. This study is aimed at investigating the radiopurity of Kapton for use in ultralow background, rare-event physics applications by measuring the 238U, 232Th, and natK levels using inductively coupled plasma mass spectrometry. Commercial-off-the-shelf Kapton varieties, mea- sured at approximately 950 and 120 pg/g 238U and 232Th (1.2×104 and 490 µBq/kg), respectively, can be a significant background source for many current and next-generation ultralow background detectors. This study has found that the dominant contamination is due to the use of dicalcium phosphate (DCP), a nonessential slip additive added during manufacturing. Alternative Kapton materials were obtained that did not contain DCP and were determined to be significantly more radiopure than the commercially- available options with 12 and 19 pg/g 238U and 232Th (150 and 77 µBq/kg), respectively. The lowest radioactivity version produced (Kapton ELJ, which contains an adhesive) was found to contain single digit pg/g levels of 238U and 232Th, two-to-three orders of magnitude cleaner than commercial-off-the- shelf options. Moreover, copper-clad polyimide laminates employing Kapton ELJ as the insulator were obtained and measured and showed to be very radiopure at 8.6 and 22 pg/g 238U and 232Th (110 and 89 µBq/kg), respectively.

Arnquist, Isaac J.↗
DOE OSTI2017

Cubine, a Quasi Two-Dimensional Copper–Bismuth Nanosheet

We report on the discovery of a quasi two-dimensional copper–bismuth nano sheet from ab initio calculations, which we call cubine. According to our predictions, single layers of cubine can be isolated from the recently reported high-pressure CuBi bulk material at an energetic cost of merely ≈20 meV/Å2, comparable to values to separate single layers of graphene from graphite. Our calculations suggest that cubine has remarkable electronic and electrochemical properties: It is a superconductor with a moderate electron–phonon coupling λ = 0.5, leading to Tc ≈ 1 K, and can be readily intercalated with lithium with a high diffusibility, rendering it a promising candidate material to boost the rate capacity of current electrodes in lithium-ion batteries.

Amsler, Maximilian↗
DOE OSTI2018

A Copper Relay System Involving Two Periplasmic Chaperones Drives cbb 3 -Type Cytochrome c Oxidase Biogenesis in Rhodobacter capsulatus

PccA and SenC are periplasmic copper chaperones required for the biogenesis of cbb 3 -type cytochrome c oxidase (cbb 3 -Cox) in Rhodobacter capsulatus at physiological Cu concentrations. However, both proteins are dispensable for cbb 3 -Cox assembly when the external Cu concentration is high. PccA and SenC bind Cu using Met and His residues and Cys and His residues as ligands, respectively, and both proteins form a complex during cbb 3 -Cox biogenesis. SenC also interacts directly with cbb 3 -Cox, as shown by chemical cross-linking. Here we determined the periplasmic concentrations of both proteins in vivo and analyzed their Cu binding stoichiometries and their Cu(I) and Cu(II) binding affinity constants (KD) in vitro. Our data show that both proteins bind a single Cu atom with high affinity. In vitro Cu transfer assays demonstrate Cu transfer both from PccA to SenC and from SenC to PccA at similar levels. We conclude that PccA and SenC constitute a Cu relay system that facilitates Cu delivery to cbb 3 -Cox.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Gold-Copper Nanoparticles: Nanostructural Evolution and Bifunctional Catalytic Sites

Understanding of the atomic-scale structure is essential for exploiting the unique catalytic properties of any nanoalloy catalyst. This report describes novel findings of an investigation of the nanoscale alloying of gold-copper (AuCu) nanoparticles and its impact on the surface catalytic functions. Two pathways have been explored for the formation of AuCu nanoparticles of different compositons, including wet chemical synthesis from mixed Au- and Cu-precursor molecules, and nanoscale alloying via an evolution of mixed Au- and Cu-precursor nanoparticles near the nanoscale melting temperatures. For the evolution of mixed precursor nanoparticles, synchrotron x-ray based in-situ real time XRD was used to monitor the structural changes, revealing nanoscale alloying and reshaping towards an fcc-type nanoalloy (particle or cube) via a partial melting–resolidification mechanism. The nanoalloys supported on carbon or silica were characterized by in-situ high-energy XRD/PDFs, revealing an intriguing lattice "expanding-shrinking" phenomenon depending on whether the catalyst is thermochemically processed under oxidative or reductive atmosphere. This type of controllable structural changes is found to play an important role in determining the catalytic activity of the catalysts for carbon monoxide oxidation reaction. The tunable catalytic activities of the nanoalloys under thermochemically oxidative and reductive atmospheres are also discussed in terms of the bifunctional sites and the surface oxygenated metal species for carbon monoxide and oxygen activation.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2014

Evolution of a plant-specific copper chaperone family for chloroplast copper homeostasis

Metallochaperones traffic copper (Cu + ) from its point of entry at the plasma membrane to its destination. In plants, one destination is the chloroplast, which houses plastocyanin, a Cu-dependent electron transfer protein involved in photosynthesis. In this paper, we present a previously unidentified Cu + chaperone that evolved early in the plant lineage by an alternative-splicing event of the pre-mRNA encoding the chloroplast P-type ATPase in Arabidopsis 1 (PAA1). In several land plants, recent duplication events created a separate chaperone-encoding gene coincident with loss of alternative splicing. The plant-specific Cu + chaperone delivers Cu + with specificity for PAA1, which is flipped in the envelope relative to prototypical bacterial ATPases, compatible with a role in Cu + import into the stroma and consistent with the canonical catalytic mechanism of these enzymes. The ubiquity of the chaperone suggests conservation of this Cu + -delivery mechanism and provides a unique snapshot into the evolution of a Cu + distribution pathway. Finally, we also provide evidence for an interaction between PAA2, the Cu + -ATPase in thylakoids, and the Cu + -chaperone for Cu/Zn superoxide dismutase (CCS), uncovering a Cu + network that has evolved to fine-tune Cu + distribution.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

Withanage, Wenura K.↗
NASA NTRS1973

High temperature, low cycle fatigue of copper-base alloys in argon. Part 3: Zirconium-copper; thermal-mechanical strain cycling, hold-time and notch fatigue results

The low-cycle fatigue characteristics of smooth bar and notched bar specimens (hourglass shape) of zirconium-copper, 1/2 Hard, material (R-2 Series) were evaluated at room temperature in axial strain control. Over the fatigue life range from about 300 to 3000 cycles the ratio of fatigue life for smooth bar to fatigue life for notched bar remained constant at a value of about 6.0. Some additional hold-time data for the R-2 alloy tested in argon at 538 C are reported. An analysis of the relaxation data obtained in these hold-time tests is also reported and it is shown that these data yield a fairly consistent correlation in terms of instantaneous stress rate divided by instantaneous stress. Two thermal-mechanical strain cycling tests were also performed using a cyclic frequency of 4.5 cycles per hour and a temperature cycling interval from 260 to 538 C. The fatigue life values in these tests were noticeably lower than that observed in isothermal tests at 538 C.

Conway, J. B.↗
NASA NTRS1974

High-temperature, low-cycle fatigue of advanced copper-base alloys for rocket nozzles. Part 2: NASA 1.1, Glidcop, and sputtered copper alloys

Short-term tensile and low-cycle fatigue data are reported for five advance copper-base alloys: Sputtered Zr-Cu as received, sputtered Zr-Cu heat-treated, Glidcop AL-10, and NASA alloys 1-1A and 1-1B. Tensile tests were performed in argon at 538 C using an axial strain rate of 0.002/sec. Yield strength and ultimate tensile strength data are reported along with reduction in area values. Axial strain controlled low-cycle fatigue tests were performed in argon at 538C using an axial strain rate of 0.002/sec to define the fatigue life over the range from 100 to 3000 cycles for the five materials studied. It was found that the fatigue characteristics of the NASA 1-1A and NASA 1-1B compositions are identical and represent fatique life values which are much greater than those for the other materials tested. The effect of temperature on NASA 1-1B alloy at a strain rate of 0.002/sec was evaluated along with the effect of strain rates of 0.0004 and 0.01/sec at 538 C. Hold-time data are reported for the NASA 1-1B alloy at 538 C using 5 minute hold periods in tension only and compression only at two different strain range values. Hold periods in tension were much more detrimental than hold periods in compression.

Conway, J. B.↗
DOE OSTI2018

Copper oxy-sulfide and copper sulfate thin films as transparent p-type conductive electrodes

Highlights: • Cu{sub 2}O, CuS and CuSO{sub 4} films are prepared and compared as p-type transparent electrodes. • CuSO{sub 4} gives the highest visible transmittance and CuS the lowest sheet resistance. • Cu{sub 2}O sulfurization produces CuS with a rougher surface and higher resistance. • CuS oxidation gives a Cu{sub 2}S and Cu{sub 2}O mixture with the best electrode performance. - Abstract: Starting from evaporated Cu layers, oxidation and sulfurization processes were developed by reaction at 250 °C with O{sub 2} or elemental sulfur to obtain Cu{sub 2}O and CuS thin films, respectively, with p-type conductivity and visible transparency. With the aim of achieving mixed compounds that combine the best properties of oxides (transparency) and sulfides (metal-like conductivity), different methods were tested, including Cu{sub 2}O sulfurization, CuS oxidation and direct Cu sulfoxidation. The crystalline structure, morphology and optical and electrical characteristics of the various samples were studied comparatively. CuSO{sub 4} crystals with a mean size above 40 nm were obtained by sulfoxidation, showing higher transmittance and lower resistance than the Cu{sub 2}O film shaped by crystallites of ∼13 nm. Moreover, a superior electrode quality was achieved after CuS oxidation, which produces a mixture of small Cu{sub 2}O and larger Cu{sub 2}S nanocrystals with visible transmittance as high as the pure oxide and a hole density close to the sulfide.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗