Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Cu”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43

Materials Data on Cu(NCl2)2 by Materials Project

CuCl4N2 crystallizes in the orthorhombic Cmce space group. The structure is zero-dimensional and consists of eight ammonia molecules and four CuCl4 clusters. In each CuCl4 cluster, Cu2+ is bonded in a square co-planar geometry to four Cl1- atoms. All Cu–Cl bond lengths are 2.15 Å. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Cu2+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Cu2+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Cu(RhO2)2 by Materials Project

CuRh2O4 is Spinel structured and crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Rh+3.50+ is bonded to six equivalent O2- atoms to form RhO6 octahedra that share corners with six equivalent CuO4 tetrahedra and edges with six equivalent RhO6 octahedra. All Rh–O bond lengths are 2.07 Å. Cu1+ is bonded to four equivalent O2- atoms to form CuO4 tetrahedra that share corners with twelve equivalent RhO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. All Cu–O bond lengths are 2.03 Å. O2- is bonded in a rectangular see-saw-like geometry to three equivalent Rh+3.50+ and one Cu1+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Cu(BrN3)2 by Materials Project

CuN6(Br)2 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of eight hydrobromic acid molecules and one CuN6 framework. In the CuN6 framework, Cu2+ is bonded in an octahedral geometry to six equivalent N2- atoms. All Cu–N bond lengths are 2.81 Å. N2- is bonded in a 5-coordinate geometry to one Cu2+ and four equivalent N2- atoms. All N–N bond lengths are 1.72 Å.

36 MATERIALS SCIENCE↗

Materials Data on Cu(BiO2)2 by Materials Project

CuBi2O4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.99 Å. Bi3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.36 Å) and four longer (2.72 Å) Bi–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to two equivalent Cu2+ and four equivalent Bi3+ atoms. In the second O2- site, O2- is bonded to four equivalent Bi3+ atoms to form a mixture of edge and corner-sharing OBi4 tetrahedra.

36 MATERIALS SCIENCE↗

Materials Data on Cu(IN3)2 by Materials Project

CuI2N6 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cu2+ is bonded to six equivalent N atoms to form CuN6 octahedra that share faces with eight equivalent IN12 cuboctahedra. All Cu–N bond lengths are 1.86 Å. N is bonded in a single-bond geometry to one Cu2+ and four equivalent I1- atoms. All N–I bond lengths are 2.66 Å. I1- is bonded to twelve equivalent N atoms to form IN12 cuboctahedra that share corners with twelve equivalent IN12 cuboctahedra, faces with six equivalent IN12 cuboctahedra, and faces with four equivalent CuN6 octahedra.

36 MATERIALS SCIENCE↗

Materials Data on Cu(SbO2)2 by Materials Project

CuSb2O4 crystallizes in the tetragonal P4_2bc space group. The structure is three-dimensional. Cu2+ is bonded to six O2- atoms to form distorted edge-sharing CuO6 octahedra. There are a spread of Cu–O bond distances ranging from 1.99–2.49 Å. Sb3+ is bonded in a distorted T-shaped geometry to three O2- atoms. All Sb–O bond lengths are 2.00 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cu2+ and one Sb3+ atom. In the second O2- site, O2- is bonded in a trigonal planar geometry to one Cu2+ and two equivalent Sb3+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on Cu(BrN3)2 by Materials Project

CuN6(Br)2 crystallizes in the tetragonal I4/mmm space group. The structure is one-dimensional and consists of four hydrobromic acid molecules and two CuN6 ribbons oriented in the (0, 0, 1) direction. In each CuN6 ribbon, Cu2+ is bonded in a linear geometry to two equivalent N2- atoms. Both Cu–N bond lengths are 1.83 Å. There are two inequivalent N2- sites. In the first N2- site, N2- is bonded in a distorted single-bond geometry to one Cu2+ and four equivalent N2- atoms. All N–N bond lengths are 1.65 Å. In the second N2- site, N2- is bonded in a 4-coordinate geometry to four N2- atoms. Both N–N bond lengths are 1.83 Å.

36 MATERIALS SCIENCE↗

Materials Data on Cu(N3O2)2 by Materials Project

CuN4(NO2)2 crystallizes in the monoclinic C2/m space group. The structure is zero-dimensional and consists of four nitrous acid molecules and two CuN4 clusters. In each CuN4 cluster, Cu2+ is bonded in a square co-planar geometry to four equivalent N1+ atoms. All Cu–N bond lengths are 1.83 Å. N1+ is bonded in a single-bond geometry to one Cu2+ atom.

36 MATERIALS SCIENCE↗

Stability of Cu(In x Ga 1− x )Se 2 Solar Cells Utilizing RbF Postdeposition Treatment under a Sulfur Atmosphere

Alkali halide postdeposition treatments (PDTs) have become a key tool to maximize efficiency in Cu(In x Ga 1− x )Se 2 (CIGS) photovoltaics. RbF PDTs have emerged as an alternative to the more common Na‐ and K‐based techniques. This study utilizes temperature‐dependent current–voltage ( JVT ) measurements to study a unique RbF PDT performed in a S atmosphere. The samples are measured before and after 6 months in a desiccator to study device stability. Both samples contain Na and K which diffuse from the soda–lime glass substrate. A reference sample and a RbF + S PDT sample both show the development of a rear contact barrier after aging. The contact barrier is higher for the RbF + S PDT sample, leading to decreased current in forward bias. Series resistance is also higher in the RbF + S PDT device which leads to lower fill factor. However, after aging the reference sample has a larger decrease in open‐circuit voltage ( V OC ). Ideality factor measurements suggest Shockley–Read–Hall recombination dominates both samples. V OC versus temperature and a temperature‐dependent activation energy model are used to calculate diode activation energies for each sample condition. Both techniques produce similar values that indicate recombination primarily occurs within the bulk absorber.

14 SOLAR ENERGY↗

Chemical and Electronic Structure at the Interface between a Sputter-Deposited Zn(O,S) Buffer and a Cu(In,Ga)(S,Se) 2 Solar Cell Absorber

The chemical and electronic structure of the interface between a sputter-deposited Zn(O,S) buffer layer and an industrial Cu(In,Ga)(S,Se) 2 (CIGSSe) absorber for thin-film solar cells is investigated with X-ray and UV photoelectron spectroscopy, inverse photoemission spectroscopy, and X-ray emission spectroscopy. We find a CIGSSe absorber surface band gap of 1.61 (±0.14) eV, which is significantly increased as compared to the minimal value derived with bulk-sensitive methods (≈1.1 eV). We find no indication for diffusion of absorber elements into the buffer layer. Surface- and bulk-sensitive measurements of the buffer layer suggest the presence of S-Zn and S-O bonds in the Zn(O,S) layer. We find that the naturally existing downward band bending toward the CIGSSe absorber surface is increased by the formation of the interface, likely enhancing carrier separation under illumination. We also derive a flat conduction band alignment, in line with the reported high conversion efficiencies of corresponding large-area solar cells.

14 SOLAR ENERGY↗

Combinatorial Synthesis and High-Throughput Characterization of Microstructure and Phase Transformation in Ni–Ti–Cu–V Quaternary Thin-Film Library

Ni–Ti–based shape memory alloys (SMAs) have found widespread use in the last 70 years, but improving their functional stability remains a key quest for more robust and advanced applications. Named for their ability to retain their processed shape as a result of a reversible martensitic transformation, SMAs are highly sensitive to compositional variations. Alloying with ternary and quaternary elements to fine-tune the lattice parameters and the thermal hysteresis of an SMA, therefore, becomes a challenge in materials exploration. Combinatorial materials science allows streamlining of the synthesis process and data management from multiple characterization techniques. In this study, a composition spread of Ni–Ti–Cu–V thin-film library was synthesized by magnetron co-sputtering on a thermally oxidized Si wafer. Composition-dependent phase transformation temperature and microstructure were investigated and determined using high-throughput wavelength dispersive spectroscopy, synchrotron X-ray diffraction, and temperature-dependent resistance measurements. Of the 177 compositions in the materials library, 32 were observed to have shape memory effect, of which five had zero or near-zero thermal hysteresis. These compositions provide flexibility in the operating temperature regimes that they can be used in. A phase map for the quaternary system and correlations of functional properties are discussed with respect to the local microstructure and composition of the thin-film library.

42 ENGINEERING↗

MgO Nanostructures on Cu(111): Understanding Size- and Morphology-Dependent CO 2 Binding and Hydrogenation

To design and optimize cost-effective technologies for the capture, utilization, and storage of carbon dioxide (CO 2 ), we need a fundamental knowledge and control of chemical interactions associated with the capture and conversion of the molecule into high-value chemicals, minerals, and all kinds of materials. Bulk magnesium oxide (MgO) is frequently used for the trapping and storage of CO 2 by generation of magnesium carbonates. In this study, the growth and reactivity of MgO nanostructures on a Cu 2 O/Cu(111) substrate were investigated using scanning tunneling microscopy (STM) and synchrotron-based ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). For extremely small concentrations of Mg (~ 0.01 monolayer (ML)), a well-ordered film of copper oxide with small clusters (0.2-0.5 nm in width, 0.4-0.6 Å in height) of embedded MgO was seen. At a coverage of 0.1 ML, MgO nanoparticles with a width of 0.4 to 1 nm and a height of ~ 1.5 Å were randomly distributed on the copper oxide. Further, random distribution was also observed when the MgO coverage was raised to 0.25 ML, with the width of the MgO particles increasing to 2-2.5 nm and the height reaching 2 Å. These oxide nanostructures displayed a high reactivity towards CO 2 and H 2 that is not seen for bulk MgO. Dissociation of H 2 was observed at room temperature with reaction of the H adatoms with CuO x and C-containing groups. On the small MgO nanostructures (< 1 nm in width), instead of plain carbonate formation, there was dissociation of CO 2 into CO and C species, opening reaction channels for the conversion of this harmful molecule into oxygenates and light alkanes.

03 NATURAL GAS↗

Screening Cu-Zeolites for Methane Activation Using Curriculum-Based Training

Machine learning (ML), when used synergistically with atomistic simulations, has recently emerged as a powerful tool for accelerated catalyst discovery. However, the application of these techniques has been limited by the lack of interpretable and transferable ML models. In this work, we propose a curriculum-based training (CBT) philosophy to systematically develop reactive machine learning potentials (rMLPs) for high-throughput screening of zeolite catalysts. Our CBT approach combines several different types of calculations to gradually teach the ML model about the relevant regions of the reactive potential energy surface. The resulting rMLPs are accurate, transferable, and interpretable. We further demonstrate the effectiveness of this approach by exhaustively screening thousands of [CuOCu] 2+ sites across hundreds of Cu-zeolites for the industrially relevant methane activation reaction. Specifically, this large-scale analysis of the entire International Zeolite Association (IZA) database identifies a set of previously unexplored zeolites (i.e., MEI, ATN, EWO, and CAS) that show the highest ensemble-averaged rates for [CuOCu] 2+ -catalyzed methane activation. We believe that this CBT philosophy can be generally applied to other zeolite-catalyzed reactions and, subsequently, to other types of heterogeneous catalysts. Thus, this represents an important step toward overcoming the long-standing barriers within the computational heterogeneous catalysis community.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Precursor Reaction Method With High Ga Cu(In,Ga)(S,Se)$_{2}$ to Achieve Increased Open-Circuit Voltage

The precursor reaction process for the fabrication of Cu(In,Ga)Se 2 solar cells potentially allows for low-cost fabrication and scalable processing for manufacturing. Additionally, this process has yielded record efficiencies in lab-scale experiments. Thus far, research on the precursor reaction method has been restricted to relatively low Ga compositions with Ga/(In+Ga) ≈ 25%. By increasing the ratio of Ga, it is possible to increase the bandgap, and thus, increase the open-circuit voltage. This work develops and characterizes the precursor reaction process for use with Ga/(In+Ga) ≈ 50%, with the goal of improving the open-circuit voltage and efficiency. It is shown that with an increased Ga ratio, increased V ∞ is achieved, but the rate of conversion from the precursor to absorber phases is decreased. Additionally, increased Ga improves the film adhesion at increased selenization temperatures as well as improving the film morphology.

14 SOLAR ENERGY↗

Evaluating Recombination Mechanisms in RbF Treated Cu(In${}_\mathrm{x}$Ga$_\mathrm{1-x}$)Se$_{2}$ Solar Cells

Rubidium fluoride (RbF) postdeposition treatment (PDT) has been shown to improve the performance of Cu(In x Ga 1-x )Se 2 (CIGS) photovoltaic devices. Here, in this study, temperature-dependent current voltage (JVT) and time-resolved photoluminescence (TRPL) experiments were combined with modeling using the solar cell capacitance simulator (SCAPS) computer code to investigate the effect of the RbF PDT. Two devices, one as-deposited and one with RbF PDT, were deposited by a three stage coevaporation process. JVT measurements suggest the dominant recombination mechanism may be tunneling-enhanced recombination via bandtail states, but that defect states in the bandgap can also be important. RbF PDT is shown to decrease the characteristic energy of the bandtails. TRPL data show an increase in the minority carrier lifetime after RbF PDT, leading to an improved open-circuit voltage. SCAPS modeling indicates that the dominant recombination mechanism is dependent on the specific defect makeup of a device, suggesting that small changes in processing conditions can impact device behavior. This explains the observation that, for some devices, defect states in the gap dominate while others, as is the case here, appear to be dominated by bandtails.

14 SOLAR ENERGY↗

Improved VOC in RbF-Treated Cu(In,Ga)Se2 Solar Cells via Passivation of Recombination Centers

Cu(In,Ga)Se 2 (CIGS) solar cells have benefited in recent years from the addition of heavy alkali elements, such as Rb, which increase the solar cell open-circuit voltage ( V OC ). To investigate the source of this improvement, here, we compare samples with and without Rb to perform a quantitative comparison of electronic defects and minority carrier lifetime. Deep-level transient and optical spectroscopy measurements were performed on two sets of rubidium fluoride (RbF)-treated and untreated CIGS, and three distinct traps were identified regardless of RbF treatment. The RbF treatment was found to reduce the concentration of the H2 trap, which was previously found to act as a recombination center and is located preferentially at CIGS grain boundaries. Time-resolved photoluminescence measurements showed an increase in effective lifetime after RbF and nearly all lifetime improvement resulted from reductions in bulk recombination. The observed V OC improvement is well correlated with increased minority carrier lifetime and acceptor concentration, which led to increases and decreases in electron and hole quasi-Fermi levels, respectively.

Cu(In Ga)Se2 (CIGS)↗

The Effects of Absorber Thickness on Reverse-Bias Damage in Cu(In,Ga)Se2 Solar Cells

We studied a variety of absorber thicknesses in Cu(In,Ga)Se 2 devices to examine the ability of the cell to withstand reverse current flow without damage. Absorbers were varied from 2.5 um to 0.4 um, with the expectation that larger reverse current would be allowed to flow at lower voltages as absorbers were made thinner. Our initial experiments showed promise. However, as the efficiency of thin devices was improved, the reverse current allowed at a given voltage decreased. Here we present our negative results on the ability of thin devices to allow higher reverse currents at lower voltages. We also give details on our procedures for reverse-bias testing small-area solar cells. We hope this information will be useful for those who want to study reverse-bias at the cell level.

14 SOLAR ENERGY↗

On the Effect of Indium Chloride Dose on the Recrystallization of Cu(In,Ga)Se 2 Thin Films and associated Devices

Cu(In,Ga)Se 2 thin films deposited by a single-stage co-evaporation process at 350 ºC on molybdenum coated soda lime glass substrate were annealed post-deposition in InCl 3 vapor. The amount of InCl 3 and Se was varied. Here, the annealing treatment was done at 450 ºC for 30 minutes. Increase in grain size was observed after the treatment in all cases by X-ray diffraction. Device performance was low, but improved slightly after KCN etching.

14 SOLAR ENERGY↗