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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Properties of interfaces between copper and copper sulphide/oxide films

We compare different means of predicting and rationalizing properties of corrosion films aiming at gaining deeper understanding of the behaviour of copper in aqueous and sulphide-containing environments. Purely geometrical tools ranging from mean bulk information to anisotropic and facet-specific approaches are discussed, and their performances compared against DFT-based stability and property evaluations of a range of interfaces arising from combining low-index crystallographic planes of the compounds Cu, Cu 2 O, and Cu 2 S. We demonstrate the necessity to consider facet-specific interactions to understand nanolevel differences between Cu 2 S and Cu 2 O film behaviour, and that thin films cannot be directly described by bulk properties.

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

An Efficient Copper-Based Redox Shuttle Bearing a Hexadentate Polypyridyl Ligand for DSCs under Low-Light Conditions

A Cu complex featuring a hexadentate ligand was synthesized and evaluated as a redox shuttle in dye-sensitized solar cell (DSC) devices, which exhibited excellent performance under low-light conditions. Cu-based redox shuttles (RSs) have been shown to perform remarkably well under low-light conditions; however, most of the known Cu-based RSs employ bidentate pyridyl ligands and often require bulky flanking groups adjacent to the nitrogen donors of these ligands to prevent distortion and binding of exogenous Lewis bases such as 4- tert -butylpyridine (TBP) that are added to enhance cell performance. Without the bulky substituents, the bidentate ligands are susceptible to ligand exchange with TBP. In this context, we have developed a Cu-based RS with a preorganized multidentate ligand designed to facilitate efficient electron transfer kinetics and high stability via the chelate effect. The Cu system, [Cu(bpyPY4)] 2+/+ , reported here is supported by the hexadentate polypyridyl ligand bpyPY4 (6,6'-bis(1,1-di(pyridine-2-yl)ethyl)-2,2'-bipyridine) and examined as a RS in DSCs. From X-ray crystallography and variable-temperature 1 H NMR studies, bpyPY4 provides a dynamic coordination environment around the metal center. Cyclic voltammetry and UV–visible and NMR spectroscopy indicate that noncoordinated pyridyl donors block binding of TBP to copper. DSC devices using [Cu(bpyPY4)] 2+/+ as the redox electrolyte gave a power conversion efficiency (PCE) value of 4.9% under 1 sun illumination (100 mW/cm 2 ). Strikingly, the device performance increased to 11.11% when irradiated with 2400 lux (0.5 mW/cm 2 ) via a fluorescent lamp light source and improved further to 15.2% PCE at 13500 lux (2.10 mW/cm 2 ). In conclusion, the Cu redox shuttle is an intriguing candidate for implementation with narrow band gap sensitizers with low oxidation potentials, which are important for high photocurrent DSC devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Thermal Stability of Copper–Nickel and Copper–Nickel Silicide Contacts for Crystalline Silicon

Copper is a low-cost, low-damage alternative to Ag paste for front-side metallization of crystalline Si (c-Si) solar cells, but requires conductive diffusion barriers like Ni or NiSi. Thermal stability of these barriers during postmetallization anneal is critical for performance. In this study, we address the structural and chemical stability of Cu contacts with both Ni and NiSi barrier layers, identifying interfacial reactions responsible for their degradation. Superior thermal and chemical stability of single-phase NiSi barrier as compared to Ni is made evident by XRD, Auger, and Raman spectroscopies. Moreover, the commonly used Cu-Ni-Si contact stack does not convert to more stable Cu-NiSi-Si stack upon thermal treatment. Instead, Cu readily alloys with the Ni layer and reacts with the underlying c-Si to form Cu 3 Si, with no evidence for the formation of NixSi phases. Also, even the superior NiSi barrier slowly dissolves into Cu at elevated temperatures.

14 SOLAR ENERGY↗
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 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↗