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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Effect of Co-Reactants on Interfacial Oxidation in Atomic Layer Deposition of Oxides on Metal Surfaces

We have examined the ALD of Al 2 O 3 using TMA as the precursor and t-BuOH and H 2 O as the co-reactants, focusing on the effects of the latter on both the ALD process and the possible modification of the underlying substrate. We have employed a quartz-crystal microbalance (QCM) to monitor ALD in situ and in real-time, and the deposited thin films have been characterized using X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and X-ray reflectivity. Growth of thin films of Al 2 O 3 using TMA and either t-BuOH or H 2 O as the co-reactant at T = 285 °C produces thin films of similar physical properties (density, stoichiometry, minimal carbon incorporation), and the growth rate per cycle is similar for the two co-reactants at this temperature. At a lower temperature of T = 120 °C, the behavior is starkly different, where growth occurs with H 2 O but not with t-BuOH. At either process temperature, we find no evidence for significant coverages of a long-lived tert-butoxy species from the reaction of t-BuOH. Deposition of thin films of Al 2 O 3 on metal surfaces of Cu and Co has been examined for evidence of interfacial oxidation. While growth with either co-reactant does not lead to the oxidation of the underlying Cu substrate, use of H 2 O leads to the oxidation of Co, while use of t-BuOH as the co-reactant does not. Thermodynamic factors may affect early stages of growth as Al species will likely scavenge all free O species. In contrast, at later times diffusion of species through the deposited Al 2 O 3 thin film could result in oxidation at the Al 2 O 3 |metal interface, a process that is strongly hindered in the case of t-BuOH due to its size. Furthermore, this observation highlights the importance of the choice of the co-reactant concerning ALD of oxides on metal surfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2Cu5TeS3O19 by Materials Project

Na2Cu5TeS3O19 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.33–2.85 Å. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.94 Å. There are three inequivalent Cu+2.40+ sites. In the first Cu+2.40+ site, Cu+2.40+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share corners with three SO4 tetrahedra and edges with two CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.79–2.55 Å. In the second Cu+2.40+ site, Cu+2.40+ is bonded in a 6-coordinate geometry to five O2- atoms. There are a spread of Cu–O bond distances ranging from 1.80–2.49 Å. In the third Cu+2.40+ site, Cu+2.40+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share corners with two equivalent SO4 tetrahedra and edges with two equivalent CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.84–2.55 Å. Te6+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Te–O bond distances ranging from 1.93–2.54 Å. There are two inequivalent S6+ sites. In the first S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with two equivalent CuO6 octahedra. The corner-sharing octahedra tilt angles range from 43–55°. There are a spread of S–O bond distances ranging from 1.46–1.55 Å. In the second S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with four CuO6 octahedra. The corner-sharing octahedra tilt angles range from 48–52°. There is three shorter (1.49 Å) and one longer (1.51 Å) S–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two equivalent Cu+2.40+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Cu+2.40+, and one S6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Te6+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one S6+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Cu+2.40+ and one S6+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Cu+2.40+, and one S6+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to one Na1+ and one S6+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Cu+2.40+, and one Te6+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, two Cu+2.40+, and one S6+ atom. In the tenth O2- site, O2- is bonded in a water-like geometry to two equivalent Cu+2.40+ atoms. In the eleventh O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Cu+2.40+ atoms. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Cu+2.40+, and one Te6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Microstructural Characterization of the Second High Fluence Baffle-Former Bolt Retrieved from a Westinghouse Two-loop Downflow Type PWR

As one of the pressurized water reactor (PWR) internal components, baffle-former bolts (BFBs) are subjected to significant mechanical stress and neutron irradiation from the reactor core during the plant operation. Over the long operation period, these conditions lead to potential degradation and reduced load-carrying capacity of the bolts. In support of evaluating long-term operational performance of materials used in core internal components, the Oak Ridge National Laboratory (ORNL), through the Department of Energy (DOE), Light Water Reactor Sustainability (LWRS) Program, Materials Research Pathway (MRP) has harvested two high fluence BFBs from a commercial Westinghouse two-loop downflow type PWR. The two bolts of interest, i.e. bolts # 4412 and 4416, were withdrawn from service in 2011 as part of a preventative replacement plan. No identification of cracking or potential damage was found for these bolts during their removal in 2011. However, the bolts required a lower torque for removal from the baffle structure than the original torque specified during installation. Irradiation displacement damage levels in the bolts range from 15 to 41 displacements per atom. The goal of this project is to perform detailed microstructural and mechanical property characterization of BFBs following in-service exposures. The information from these bolts will be integral to the LWRS program initiatives in evaluating end of life microstructure and properties. Furthermore, valuable data will be obtained that can be incorporated into model predictions of long-term irradiation behavior and compared to results obtained in high flux experimental reactor conditions. In this report, we present our latest study in FY22 on microstructural characterizations of the second high fluence baffle-former bolt, i.e., bolt # 4412. Analytical electron microscopy and atom probe tomography characterization were performed. The radiation-induced defects in the material add to the large wealth of knowledge for neutron-induced defects in 304/316 grades of stainless steels, specifically for radiation-induced precipitation after high fluence commercial PWR irradiation. The main findings are summarized as follows: 1) The cavity size was considerably larger in the bolt thread section than in the bolt head, with the bolt thread section having a bimodal distribution of cavities greater than ~6 nm in diameter and less than ~3 nm in diameter. The bolt head only had the small-sized cavities. In addition, there was a denuded zone of large cavities near grain boundaries in the thread section of the bolt. 2) Radiation-induced precipitation in the BFB #4412 was highly complex, with the volume fraction, size, and number density of Ni/Si and Cu-rich precipitates depending strongly on the radiation temperature/dose. In many cases, co-precipitates of adjoined clusters were found with Ni/Si-rich precipitates sandwiched between Cu-rich clusters and Mo/Cr/P-rich clusters. 3) Solute segregation out of solution was highest for most solutes in the thread section of the bolt #4412 with the exception of Cu, which experienced more separation out of solution into Curich clusters in the bolt head section. This highlights the difference in the mechanisms for precipitation of Ni/Si clusters, which have the Ni 3 Si phase composition, and precipitation of Cu-rich clusters. 4) There appear to be multiple simultaneous influences that affect the microstructural variation along the length of the bolt that overcomes the ~2X difference in irradiation dose between the bolt head and the bolt thread. The irradiation temperature, thermal/fast neutron ratio variation, potential strain gradient, and exposure to PWR coolant water that each section of the bolt sees may have more influence on the microstructural evolution than the total irradiation dose. The bolt thread and shank, with higher temperature, higher relative fast neutron flux, higher strain, and exposure to coolant but lower dose, underwent more enhanced cavity formation, precipitation, and solute segregation than the bolt head section.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS2014

The O/OREOS Mission - Astrobiology in Low Earth Orbit

The O/OREOS (Organism/Organic Exposure to Orbital Stresses) nanosatellite is the first science demonstration spacecraft and flight mission of the NASA Astrobiology Small- Payloads Program (ASP). O/OREOS was launched successfully on November 19, 2010, to a high-inclination (72 deg), 650-km Earth orbit aboard a US Air Force Minotaur IV rocket from Kodiak, Alaska. O/OREOS consists of 3 conjoined cubesat (each 1000 cu cm) modules: (i) a control bus; (ii) the Space Environment Survivability of Living Organisms (SESLO) experiment; and (iii) the Space Environment Viability of Organics (SEVO) experiment. Among the innovative aspects of the O/OREOS mission are a real-time analysis of the photostability of organics and biomarkers and the collection of data on the survival and metabolic activity for microorganisms at 3 times during the 6-month mission. We report on the spacecraft characteristics, payload capabilities, and present operational phase and flight data from the O/OREOS mission. The science and technology rationale of O/OREOS supports NASA0s scientific exploration program by investigating the local space environment as well as space biology relevant to Moon and Mars missions. It also serves as a precursor for experiments on small satellites, the International Space Station (ISS), future free-flyers and lunar surface exposure facilities.

Spectroscopy↗
DOE OSTI2022

ACuZrQ 3 (A = Rb, Cs; Q = S, Se, Te): Direct Bandgap Semiconductors and Metals with Ultralow Thermal Conductivity

ACuZrQ 3 (A = Rb, Cs; Q = S, Se, Te) were synthesized as black platelet crystals. RbCuZrS 3 , RbCuZrSe 3 , and CsCuZrS 3 crystallize in the KCuZrSe 3 structure type with space group Cmcm, and RbCuZrTe 3 and CsCuZrTe 3 crystallize in the lower symmetry space group Pnma. The tellurides exhibit a second order Jahn-Teller distortion with off-centering of Zr in its octahedral environment. The magnitude of the distortion is larger in RbCuZrTe 3 than in CsCuZrTe 3 . The structures of beta-CsCuS 4 and Rb 2 Cu 5 Te 5 were also determined. CsCuZrS 3 melts at 910 C-circle and exhibits partial decomposition upon heating at 275 C-circle, while CsCuZrTe 3 melts incongruently. Our DFT calculations of RbCuZrQ 3 (Q = S, Se) and CsCuZrS 3 indicate direct gap semiconductors in agreement with experiments. ACuZrTe 3 (A = Rb, Cs) were calculated to be metals which was confirmed for RbCuZrTe 3 with variable temperature conductivity measurements and consistent with heat capacity measurements. Spectroscopic measurements found a bandgap and work function of 1.44(5) eV and 4.89(5) eV for RbCuZrS 3 and 0.95(5) eV and 4.67(5) eV for RbCuZrSe 3 , respectively. Finally, RbCuZrTe 3 did not exhibit an optical bandgap and has a work function of 4.64(5) eV. RbCuZrTe 3 exhibits a low thermal conductivity under 0.5 W m -1 K -1 at room temperature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

G 0 W 0 Ionization Potentials of First-Row Transition Metal Aqua Ions

Here, we report computations of the vertical ionization potentials within the GW approximation of the near-complete series of first-row transition metal (V–Cu) aqua ions in their most common oxidation states, i.e., V 3+ , Cr 3+ , Cr 2+ , Mn 2+ , Fe 3+ , Fe 2+ , Co 2+ , Ni 2+ , and Cu 2+ . The d-orbital occupancy of these systems spans a broad range from d 2 to d 9 . All of the structures were first optimized at the density functional theory level using a large cluster of explicit water molecules that are embedded in a continuum solvation model. Vertical ionization potentials were computed with the one-shot G 0 W 0 approach on a range of transition metal ion clusters (6, 18, 40, and 60 explicit water molecules), wherein the convergence with respect to the basis set size was evaluated using the systems with 40 water molecules. We assess the results using three different density functional approximations as starting points for the vertical ionization potential calculations, namely, G 0 W 0 @PBE, G 0 W 0 @PBE0, and G 0 W 0 @r 2 SCAN. While the predicted ground-state structures are similar to all three exchange-correlation functionals, the vertical ionization potentials were in closer agreement with experiment when using the G 0 W 0 @PBE0 and G 0 W 0 @r 2 SCAN approaches, with the r 2 SCAN-based calculations being significantly less expensive. Computed bond distances and vertical ionization potentials for all structures are in good agreement with available experimental data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

A new series of oxycarbonate superconductors (Cu(0.5)C(0.5))(m)Ba(m+1)Ca(n-1)Cu(n)O2(m+n)+1

We found a new series of oxycarbonate superconductors in the Ba-CaCu-C-O system under high pressure of 5 GPa. Their ideal formula is (Cu(0.5)C(0.5)(m)Ba(m+1)Ca(n-1)Cu(n)O2)((m+n)+1) ((Cu,C)-m(m+1)(n-1)n). Thus far, n = 3, 4 members of the m = 1 series, (Cu,C)-1223 and (Cu,C)-1234, have been prepared in bulk while n = 4, 5 members, (Cu,C)-2334 and (Cu,C)-2345, have been prepared for the m = 2 series. (Cu,C)-1223 shows superconductivity below 67 K while T(sub c)'s of other compounds are above 110 K. In particular, (Cu,C)-1234 has the highest T(sub c) of 117 K.

Takayama-Muromachi, E.↗
DOE OSTI2020

Materials Data on K3(CuS)4 by Materials Project

K3(CuS)4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six S2- atoms to form a mixture of distorted corner, edge, and face-sharing KS6 octahedra. The corner-sharing octahedra tilt angles range from 36–64°. There are a spread of K–S bond distances ranging from 3.24–3.34 Å. In the second K1+ site, K1+ is bonded to six S2- atoms to form a mixture of distorted corner and edge-sharing KS6 octahedra. The corner-sharing octahedra tilt angles range from 36–46°. There are four shorter (3.17 Å) and two longer (3.23 Å) K–S bond lengths. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a trigonal planar geometry to three S2- atoms. There are two shorter (2.27 Å) and one longer (2.30 Å) Cu–S bond lengths. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a distorted trigonal planar geometry to four S2- atoms. There are a spread of Cu–S bond distances ranging from 2.33–3.00 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to five K1+ and three Cu+1.25+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to four K1+ and four Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu6CuTe2 by Materials Project

Lu6CuTe2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are six inequivalent Lu sites. In the first Lu site, Lu is bonded in a 4-coordinate geometry to four Te atoms. There are two shorter (3.08 Å) and two longer (3.09 Å) Lu–Te bond lengths. In the second Lu site, Lu is bonded in a 5-coordinate geometry to three equivalent Cu and two equivalent Te atoms. There are two shorter (2.91 Å) and one longer (3.10 Å) Lu–Cu bond lengths. Both Lu–Te bond lengths are 3.18 Å. In the third Lu site, Lu is bonded in a 3-coordinate geometry to two equivalent Cu and one Te atom. Both Lu–Cu bond lengths are 2.86 Å. The Lu–Te bond length is 3.20 Å. In the fourth Lu site, Lu is bonded in a 4-coordinate geometry to one Cu and four Te atoms. The Lu–Cu bond length is 3.47 Å. There are a spread of Lu–Te bond distances ranging from 3.03–3.26 Å. In the fifth Lu site, Lu is bonded to two equivalent Cu and three Te atoms to form distorted edge-sharing LuCu2Te3 trigonal bipyramids. Both Lu–Cu bond lengths are 2.84 Å. There are one shorter (3.04 Å) and two longer (3.12 Å) Lu–Te bond lengths. In the sixth Lu site, Lu is bonded in a 1-coordinate geometry to one Cu and one Te atom. The Lu–Cu bond length is 3.34 Å. The Lu–Te bond length is 3.07 Å. Cu is bonded in a 9-coordinate geometry to nine Lu atoms. There are two inequivalent Te sites. In the first Te site, Te is bonded in a 7-coordinate geometry to seven Lu atoms. In the second Te site, Te is bonded in a 8-coordinate geometry to eight Lu atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Comparison of two weighted integration models for the cueing task: linear and likelihood

In a task in which the observer must detect a signal at two locations, presenting a precue that predicts the location of a signal leads to improved performance with a valid cue (signal location matches the cue), compared to an invalid cue (signal location does not match the cue). The cue validity effect has often been explained with a limited capacity attentional mechanism improving the perceptual quality at the cued location. Alternatively, the cueing effect can also be explained by unlimited capacity models that assume a weighted combination of noisy responses across the two locations. We compare two weighted integration models, a linear model and a sum of weighted likelihoods model based on a Bayesian observer. While qualitatively these models are similar, quantitatively they predict different cue validity effects as the signal-to-noise ratios (SNR) increase. To test these models, 3 observers performed in a cued discrimination task of Gaussian targets with an 80% valid precue across a broad range of SNR's. Analysis of a limited capacity attentional switching model was also included and rejected. The sum of weighted likelihoods model best described the psychophysical results, suggesting that human observers approximate a weighted combination of likelihoods, and not a weighted linear combination.

NASA Program Biomedical Research and Countermeasur↗
DOE OSTI2024

Benchmarking nitrous oxide adsorption and activation in metal–organic frameworks bearing coordinatively unsaturated metal centers

Anthropogenic emissions of N 2 O, the third most abundant greenhouse gas after CO 2 and CH 4 , are contributing to global climate change. Although metal–organic frameworks (MOFs) have been widely studied as adsorbents for CO 2 and CH 4 , less effort has focused on the use of MOFs to remove N 2 O from emission streams or from air. Further, N 2 O activation would enable its use as an inexpensive oxidant for fine chemical synthesis. Here, in this paper, we identify features that contribute to strong binding and high uptake of N 2 O at coordinatively unsaturated metal sites in the M 2 Cl 2 (btdd) (M = Mn, Co, Ni, Cu; btdd 2– = bis(1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin) and M 2 (dobdc) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn; dobdc 4– = 2,5-dioxido-1,4-benzenedicarboxylate) series of MOFs. Combined experimental and computational studies suggest that N 2 O adsorption at open-metal-sites is primarily based on electrostatic interactions, rather than π-backbonding, causing MOFs with more Lewis acidic metal centers to be superior N 2 O adsorbents. As a result, Mg 2 (dobdc) demonstrates strong binding and record-setting N 2 O uptake (8.75 mmol g –1 at 1 bar and 298 K). Using density functional theory (DFT) to characterize reactive intermediates and transition states, we demonstrate that N 2 O activation to form a M(IV)–oxo species and N 2 is thermodynamically favorable in Mn 2 (dobdc) and Fe 2 (dobdc) but appears to be kinetically limited in Mn 2 (dobdc). Our work lays a foundation for understanding N 2 O adsorption and activation in MOFs, paving the way for the design of promising next-generation materials for N 2 O capture and utilization.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Energetic particle-induced enhancements of stratospheric nitric acid

Inclusion of complete ion chemistry in the calculation of minor species production during energetic particle deposition events leads to significant enhancement in the calculated nitric acid concentration during precipitation. An ionization rate of 1.2 x 10(exp 3)/cu cm/s imposed for 1 day increases HNO3 from 3 x 10(exp 5) to 6 x 10(exp 7)/cu cm at 50 km. With an ionization rate of 600 cu cm/s, the maximum HNO3 is 3 x 10(exp 7)/cu cm. Calculations which neglect negative ions predict the nitric acid will fall during precipitation events. The decay time for converting HNO3 into odd nitrogen and hydrogen is more than 1 day for equinoctial periods at 70 deg latitude. Examination of nitric acid data should yield important information on the magnitude and frequency of charged particle events.

Aikin, Arthur C.↗
DOE OSTI2020

Materials Data on MgAl2Cu by Materials Project

Al2CuMg crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Mg is bonded in a 1-coordinate geometry to three equivalent Cu and ten equivalent Al atoms. There are one shorter (2.65 Å) and two longer (2.82 Å) Mg–Cu bond lengths. There are six shorter (3.04 Å) and four longer (3.12 Å) Mg–Al bond lengths. Cu is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Al atoms. There are two shorter (2.51 Å) and four longer (2.54 Å) Cu–Al bond lengths. Al is bonded in a 3-coordinate geometry to five equivalent Mg and three equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Adsorbate-induced adatom formation on Au-Cu bimetallic alloys and its possible consequences for CO 2 electroreduction

The adsorbate-induced formation of sub-nanometer clusters on transition-metal single crystals observed in previous high-pressure microscopic studies hinted at the in-situ formation of unique active sites even on large nanoparticle catalysts. We propose that the adatom formation energy can be used as an energetic descriptor for the initial step toward the adsorbate-induced metal-cluster formation process. This descriptor can be efficiently computed using density functional theory (DFT) calculations and applied for screening and identification of metal catalysts where this phenomenon may play an important role in generating active sites in-situ. As a proof of concept, here, we construct an adatom formation energy database for three Au x Cu y alloys (x:y = 3:1, 1:1, or 1:3) and eighteen adsorbates (H, C, N, O, F, S, Cl, Br, I, CH x , NH x (x = 1 – 3), CO, NO, and OH) commonly involved in catalytic reactions. The energetics of adatom formation were examined in all cases where the (111) terrace, (211) step-edge, and (874) kink were the sources of the adatom. We demonstrate that the presence of an adsorbate could alter not only the energetics for adatom formation but also the elemental nature of the preferred adatom being formed. Using our database, we identified promising systems which favor adsorbate-induced adatom formation under near-ambient conditions. Specifically, CO-induced adatom formation on all three Au-Cu alloy surfaces could occur under CO 2 electroreduction (CO 2 RR) conditions. This phenomenon offers a qualitative explanation for the experimentally observed CO 2 RR activity on Au-Cu alloy catalysts. As a result, our methodology offers an easily expandable and efficient approach for large-scale catalyst screening with regards to adatom/cluster formation under reaction conditions and provides insight into the possible nature of active sites on alloy catalysts from a novel perspective.

Active site↗
DOE OSTI2022

All-atmospheric fabrication of Ag–Cu core–shell nanowire transparent electrodes with Haacke figure of merit >600 × 10–3 Ω−1

Abstract Transparent conducting electrodes (TCEs) are essential components in devices such as touch screens, smart windows, and photovoltaics. Metal nanowire networks are promising next-generation TCEs, but best-performing examples rely on expensive metal catalysts (palladium or platinum), vacuum processing, or transfer processes that cannot be scaled. This work demonstrates a metal nanowire TCE fabrication process that focuses on high performance and simple fabrication. Here we combined direct and plating metallization processes on electrospun nanowires. We first directly metallize silver nanowires using reactive silver ink. The silver catalyzes subsequent copper plating to produce Ag–Cu core–shell nanowires and eliminates nanowire junction resistances. The process allows for tunable transmission and sheet resistance properties by adjusting electrospinning and plating time. We demonstrate state-of-the-art, low-haze TCEs using an all-atmospheric process with sheet resistances of 0.33 Ω sq −1 and visible light transmittances of 86% (including the substrate), leading to a Haacke figure of merit of 652 × 10 –3 Ω −1 . The core–shell nanowire electrode also demonstrates high chemical and bending durability.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hybrid Mesoporous Carbon/Copper Ferrite Electrode for Asymmetric Supercapacitors

Asymmetric supercapacitors (ASCs) with two dissimilar electrodes are known to exhibit relatively moderate energy and power densities. If electrodes derived from earth-abundant materials or renewable resources such as lignocellulosic biomass (LCB) are used for fabrication, energy storage systems are expected to become less expensive and more sustainable. Hybrid electrode materials have advantages such as higher surface area, better chemical stability, and superior energy density. This study reports on the synthesis of a novel hybrid electrode material containing porous carbon (POC) and copper ferrite, which is designated as POC@Cu-ferrite, and its electrochemical performance in ASC configuration. Corn stover derived hydrochar is utilized for the sol–gel synthesis of POC@Cu-ferrite hybrid material using earth-abundant Cu and Fe-based precursors. This material is characterized using X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface area analyzer, and scanning and transmission electron microscopy (SEM/TEM). As-synthesized Cu-ferrite is found to contain 89.2% CuFe 2 O 4 and 10.8% Fe 2 O 3 , whereas other phases such as Fe 3 O 4 , CuFeO 2 , and CuO are observed for the POC@Cu-ferrite. BET-specific surface area (SSA) and pore volume of POC@Cu-ferrite are observed as 1068 m 2 /g and 0.72 cm 3 /g, respectively. POC@Cu-ferrite hybrid electrode is used with POC opposite electrode to fabricate ASC, which is tested using Gamry G-300 potentiostat/galvanostat/ZRA to obtain cyclic voltammetry (CV) profiles and galvanostatic charge–discharge (GCD) plots. ASC is also prepared using Cu-ferrite and POC materials and its specific capacitance and stability are compared with ASCs prepared with POC@Cu-ferrite and POC or graphene nanoplatelets (GNPs) electrodes. POC@Cu-ferrite hybrid electrode is found to be superior with a 2-fold higher capacitance and significant electrochemical stability over 100 GCD cycles as compared to the Cu-ferrite electrode.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-temperature lean Cu alloys with Cr-to-Nb atomic ratio of 2

Two Cu-Cr-Nb alloys, denoted as alloy 1 (comprising Cu-0.89 at% Cr-0.42 at% Nb) and alloy 2 (comprising Cu-1.84 at% Cr-0.99 at% Nb), were produced through a series of manufacturing processes including vacuum induction melting, melt spinning, consolidation, brazing, and baking, with both alloys aimed at achieving a nominal Cr-to-Nb atomic ratio of 2. Microstructural characterization using transmission electron microscopy and X-ray diffraction identified the cubic C15 Laves-phase Cr 2 Nb as the dominant precipitate in both alloys, cross-validated by thermodynamic calculations and atomistic simulation-based density functional theory (DFT). Besides cubic C15 Cr 2 Nb, hexagonal C14-phase Cr 2 Nb and α-BiF3 cubic structured Cr 3 Nb were also observed in the alloys, including a coherent interface formed between the Cr 3 Nb precipitate and the Cu matrix. The hardness of the alloys increases, and the electrical conductivity decreases with increasing alloying addition content; two practical equations described the trends. Further DFT simulations revealed that the electrical conductivity (conductance) of the Cu/Cr 2 Nb interface is an order of magnitude higher than the intrinsic Cu high-angle grain boundaries.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgCu2AsO7 by Materials Project

MgCu2AsO7 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Mg is bonded to six O atoms to form MgO6 octahedra that share corners with three equivalent AsO4 tetrahedra and edges with four CuO5 square pyramids. There are a spread of Mg–O bond distances ranging from 2.06–2.18 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded to five O atoms to form distorted CuO5 square pyramids that share a cornercorner with one CuO5 square pyramid, corners with three equivalent AsO4 tetrahedra, edges with two equivalent MgO6 octahedra, and an edgeedge with one CuO5 square pyramid. There are a spread of Cu–O bond distances ranging from 1.85–2.47 Å. In the second Cu site, Cu is bonded to five O atoms to form distorted CuO5 square pyramids that share a cornercorner with one CuO5 square pyramid, corners with two equivalent AsO4 tetrahedra, edges with two equivalent MgO6 octahedra, and an edgeedge with one CuO5 square pyramid. There are a spread of Cu–O bond distances ranging from 1.82–2.43 Å. As is bonded to four O atoms to form AsO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with five CuO5 square pyramids. The corner-sharing octahedra tilt angles range from 45–46°. There are a spread of As–O bond distances ranging from 1.68–1.75 Å. There are seven inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to two Cu and one As atom. In the second O site, O is bonded in a 3-coordinate geometry to one Mg, one Cu, and one As atom. In the third O site, O is bonded in a trigonal non-coplanar geometry to one Mg and two Cu atoms. In the fourth O site, O is bonded in a distorted trigonal planar geometry to one Mg, one Cu, and one As atom. In the fifth O site, O is bonded in a trigonal non-coplanar geometry to one Mg and two Cu atoms. In the sixth O site, O is bonded in a water-like geometry to one Mg and one Cu atom. In the seventh O site, O is bonded in a distorted trigonal planar geometry to one Mg, one Cu, and one As atom.

36 MATERIALS SCIENCE↗