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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Cryogenic properties of dispersion strengthened copper for high magnetic fields

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Isentropic expansion of copper plasma in Mbar pressure range at “Luch” laser facility

We present experimental results on thermodynamic properties of dense copper plasma in Mbar pressure range. The laser facility “Luch” with laser intensity 10{sup 14} W/cm{sup 2} is used to compress copper up to ∼8 Mbar by a strong shock wave; subsequent expansion of copper plasma into Al, Ti, Sn allows us to obtain release isentropes of copper by the impedance–matching method. A theoretical analysis and quantum simulations show that in our experiments strongly coupled quantum plasma is generated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Effect of rapid thermal processing on copper precipitation in p/p{sup +} silicon epitaxial wafers with heavily boron-doped substrates

The effect of rapid thermal processing (RTP) on the formation of copper precipitation in p/p{sup +} silicon (Si) epitaxial wafers was systematically investigated by defect etching and optical microscopy. After RTP preannealing at high temperature (1250 °C/60 s, with cooling rate 30 K/s) followed by the 750 °C/8 h + 1050 °C/16 h low-high (L-H) two-step annealing, it was revealed that the bulk microdefects were found only inside the p{sup +} substrate, manifesting no defects generated in the epitaxial layer. However, it was found that the width of denude zone (DZ) in samples only subjected to L-H two-step annealing was narrower than that of epitaxial layer, which meant that oxygen precipitation was formed in epitaxial layer. It can be concluded that RTP was beneficial to the formation of DZ. Additionally, it was found that the width of DZ has a sharp dependence on the introducing temperature of copper contamination, that is, the corresponding equilibrium concentration of interstitial copper in the Si influence the thermodynamics and kinetics process of the formation of copper precipitation significantly.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Spectral studies of copper(II) complexes of 6-(3-thienyl) pyridine-2-thiosemicarbazone

Two novel copper(II) complexes [Cu(HL)Cl]Cl.H{sub 2}O (1) and [Cu(L)NO{sub 3}]Ðœ‡H{sub 2}O (2) of the three NNS donor thiosemicarbazone ligand 6-(3-thienyl) pyridine-2-thiosemicarbazone have been synthesized. The ligand and its copper(II) complexes were characterized by elemental analysis (C, H, N, and S), FT-IR, UV-visible, magnetic susceptibility and molar conductance. The thiosemicarbazone is present either as the thione form in complex 1 or as thiol form in complex 2 and is coordinated to copper(II) atom via the pyridine nitrogen atom, the azomethine nitrogen atom and the sulfur atom. The physicochemical and spectral data suggest square planar geometry for copper(II) atoms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Formation kinetics of copper-related light-induced degradation in crystalline silicon

Light-induced degradation (LID) is a deleterious effect in crystalline silicon, which is considered to originate from recombination-active boron-oxygen complexes and/or copper-related defects. Although LID in both cases appears as a fast initial decay followed by a second slower degradation, we show that the time constant of copper-related degradation increases with increasing boron concentration in contrast to boron-oxygen LID. Temperature-dependent analysis reveals that the defect formation is limited by copper diffusion. Finally, interface defect density measurements confirm that copper-related LID is dominated by recombination in the wafer bulk.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Prediction of the critical reduced electric field strength for carbon dioxide and its mixtures with copper vapor from Boltzmann analysis for a gas temperature range of 300 K to 4000 K at 0.4 MPa

The influence of copper vapor mixed in hot CO{sub 2} on dielectric breakdown properties of gas mixture at a fixed pressure of 0.4 MPa for a temperature range of 300 K–4000 K is numerically analyzed. First, the equilibrium composition of hot CO{sub 2} with different copper fractions is calculated using a method based on mass action law. The next stage is devoted to computing the electron energy distribution functions (EEDF) by solving the two-term Boltzmann equation. The reduced ionization coefficient, the reduced attachment coefficient, and the reduced effective ionization coefficient are then obtained based on the EEDF. Finally, the critical reduced electric field (E/N){sub cr} is obtained. The results indicate that an increasing mole fraction of copper markedly reduces (E/N){sub cr} of the CO{sub 2}–Cu gas mixtures because of copper's low ionization potential and large ionization cross section. Additionally, the generation of O{sub 2} from the thermal dissociation of CO{sub 2} contributes to the increase of (E/N){sub cr} of CO{sub 2}–Cu hot gas mixtures from about 2000 K to 3500 K.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Effects of vibration frequency on vibration-assisted nano-scratch process of mono-crystalline copper via molecular dynamics simulation

It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM), especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD) model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM) potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Non-LTE analysis of neutral copper in late-type metal-poor stars

We investigated the copper abundances of 64 late-type stars in the Galactic disk and halo with effective temperatures from 5400 to 6700 K and [Fe/H] from −1.88 to −0.17. For the first time, the copper abundances are derived using both local thermodynamic equilibrium (LTE) and non-local thermodynamic equilibrium (non-LTE) calculations. High-resolution (R>40,000), high signal-to-noise ratio (S/N>100) spectra from the FOCES spectrograph are used. The atmospheric models are calculated based on the MAFAGS opacity sampling code. All the abundances are derived using spectrum synthesis methods. Our results indicate that the non-LTE effects of copper are important for metal-poor stars, showing a departure of ∼0.17 dex at a metallicity of ∼−1.5. We also find that the copper abundances derived from non-LTE calculations are enhanced compared with those from LTE. The enhancements show clear dependence on the metallicity, which gradually increases with decreasing [Fe/H] for our program stars, leading to a flatter distribution of [Cu/Fe] with [Fe/H] than previous work. There is a hint that the thick- and thin-disk stars have different behaviors in [Cu/Fe], and bending of the disk stars may exist.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Specific features of photoluminescence properties of copper-doped cadmium selenide quantum dots

The effect of doping with copper on the photoluminescence properties of cadmium selenide quantum dots 4 nm in dimension is studied. The quenching of the excitonic photoluminescence band related to the quantum dots and the appearance of an impurity photoluminescence band in the near-infrared region are observed after doping of the quantum dots with copper. It is established that, on doping of the quantum dots, the photoluminescence kinetics undergoes substantial changes. The photoluminescence kinetics of the undoped quantum dots is adequately described by a sum of exponential relaxation relations, whereas the photoluminescence kinetics experimentally observed in the region of the impurity band of the copper-doped samples follows stretched exponential decay, with the average lifetimes 0.3-0.6 {mu}s at the photon energies in the range of 1.47-1.82 eV. The experimentally observed changes in the photoluminescence properties are attributed to transformation of radiative centers in the quantum dots when doped with copper atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Morphology, optical, and adsorption properties of copper-oxide layers deposited from complex compound solutions

A technique for synthesizing gas-sensing copper-oxide layers by layer-by-layer deposition onto glass and plastic substrates is considered. Deposition is based on the oxidation of a copper–ammonia complex by hydrogen peroxide. Layers synthesized at various numbers of deposition cycles are studied by atomicforce microscopy and transmission spectroscopy methods (300–1000 nm). The spectral shape indicates the mixed nature of the oxide with predominant copper oxide (I) Cu{sub 2}O with a corresponding band gap of 2.1 eV. The layers have a continuous granular structure. The surface concentration of Brönsted acid adsorption sites with pK{sub a} ≈ 2.5 (OH acid groups), determined by the indicator method, is 560 μmol/m{sup 2} for the initial films, and threefold increases after heat treatment at 80°C for 30 min. The results obtained are interesting for the use of the described technology for fabricating copper-oxide active layers in gas-sensing sensors operating at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Majorana Electroformed Copper Mechanical Analysis

The MAJORANA DEMONSTRATOR is a large array of ultra-low background high-purity germanium detectors, enriched in 76 Ge, designed to search for zero-neutrino double-beta decay. The DEMONSTRATOR will utilize ultra high purity electroformed copper for a variety of detector components and shielding. A preliminary mechanical evaluation was performed on the Majorana prototype electroformed copper material. Several samples were removed from a variety of positions on the mandrel. Tensile testing, optical metallography, scanning electron microscopy, and hardness testing were conducted to evaluate mechanical response. Analyses carried out on the Majorana prototype copper to this point show consistent mechanical response from a variety of test locations. Evaluation shows the copper meets or exceeds the design specifications.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Results of Copper Catalyzed Peroxide Oxidation (CCPO) of Tank 48H Simulants

Savannah River National Laboratory (SRNL) performed a series of laboratory-scale experiments that examined copper-catalyzed hydrogen peroxide (H 2 O 2 ) aided destruction of organic components, most notably tetraphenylborate (TPB), in Tank 48H simulant slurries. The experiments were designed with an expectation of conducting the process within existing vessels of Building 241-96H with minimal modifications to the existing equipment. Results of the experiments indicate that TPB destruction levels exceeding 99.9% are achievable, dependent on the reaction conditions. The following observations were made with respect to the major processing variables investigated. A lower reaction pH provides faster reaction rates (pH 7 > pH 9 > pH 11); however, pH 9 reactions provide the least quantity of organic residual compounds within the limits of species analyzed. Higher temperatures lead to faster reaction rates and smaller quantities of organic residual compounds. Higher concentrations of the copper catalyst provide faster reaction rates, but the highest copper concentration (500 mg/L) also resulted in the second highest quantity of organic residual compounds. Faster rates of H 2 O 2 addition lead to faster reaction rates and lower quantities of organic residual compounds. Testing with simulated slurries continues. Current testing is examining lower copper concentrations, refined peroxide addition rates, and alternate acidification methods. A revision of this report will provide updated findings with emphasis on defining recommended conditions for similar tests with actual waste samples.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

The Jupiter Experiments: High-240 Plutonium Metal Plates Separated by Lead and Reflected by Copper

Each layer consisted of a 6 by 6 matrix of either these fuel-filled containers or solid blocks of copper of the same outer dimensions. An example of this arrangement, along with one of the copper inner reflectors, is shown in Figure 1.4. This figure shows the same aluminum containers from Figure 1.3 but with the aluminum containers completely closed. The lifting rings shown on the copper inner reflector were only for assembly and were not present for the measurement (in which the holes were filled with copper plugs). Figure 1.5 shows the loading arrangement of the aluminum containers, along with aluminum shims around the container arrays to ensure a tight fit between these layers and the surrounding reflectors. All plates were in the same orientation; none were rotated in any fashion. Additional loading information for the PAHN plates and plate loading respective to the room entrance are provided in Figures 1.6 and 1.7, respectively.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2001

Characterization of the yeast copper-inducible promoter system in Arabidopsis thaliana

Inducible promoters or gene-switches are used to both spatially and temporally regulate gene expression. Such regulation can provide information concerning the function of a gene in a developmental context as well as avoid potential harmful effects due to overexpression. A gfp construct under the control of a copper-inducible promoter was introduced into Arabidopsis thaliana (L.) Heynh. and the regulatory parameters of this inducible promoter were determined. Here, we describe the time-course of up- and down-regulation of GFP expression in response to copper level, the optimal regulatory levels of copper, and the tissue specificity of expression in three transgenic lines. We conclude that the copper-inducible promoter system may be useful in regulating the time and location of gene expression in A. thaliana.

Non-NASA Center↗
DOE OSTI2014

The molten hydrated flux synthesis of a novel open-framework copper borophosphate and its structural relation with the precursors

A novel copper borophosphate, Cu{sub 2}(H{sub 2}O)[BP{sub 2}O{sub 7}(OH)], has been synthesized by the molten hydrated flux method. Its crystal structure (Orthorhombic, Pbca, a=8.234 Å, b=9.655 Å, c=17.805 Å, V=1415.485 Å{sup 3}, Z=8) can be regarded as the condensation of alternately edge- and corner-shared copper pyramidal chains and borophosphate chains formed via vertex-sharing PO{sub 4} and BO{sub 3}(OH) tetrahedra. Magnetic measurements indicate that antiferromagnetic interactions exist in the title compound. Due to the special reaction medium created by the molten hydrated flux method, a possible structural correlation between final solids and raw materials has been discovered even though no ordered structural fragments exist in the latter. - Graphical: Structure comparison of Cu(NO{sub 3}){sub 2}·3H{sub 2}O, Cu(NO{sub 3}){sub 2}·H{sub 2}O and Cu{sub 2}(H{sub 2}O)[BP{sub 2}O{sub 7}(OH)], showing the structural evolution of CuO{sub 5} pyramids in the synthetic process. - Highlights: • A novel copper borophosphate has been synthesized by the molten hydrated flux method. • Magnetic measurements show its antiferromagnetism at low temperature. • A structural relation between the precursor and the final solid is discovered.

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

Cu{sub 2}O and CuO Films Produced by Chemical and Anodic Oxidation on the Surface of Copper Foil

The processes underlying the chemical and anodic oxidation of the surface of copper foil have been studied by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. It has been shown that, in the case of anodic oxidation, at a given process duration (τ) the composition and density of initially forming Cu(OH){sub 2} films depend not only on the current density (j{sub a}) but also on whether or not the electrolyte is stirred. A Cu{sub 2}O film with an optimal, coral-like structure has been produced by the anodic oxidation of copper foil for τ = 10 min at j{sub a} = 5 mA/cm{sup 2} without stirring, followed by the thermal reduction of the Cu(OH){sub 2} in a nitrogen atmosphere for 1 h at 500°C. In the case of the chemical oxidation of the copper foil surface, similar Cu{sub 2}O films with a coral-like structure can also be produced by the thermal reduction of initially forming Cu(OH){sub 2} at 500°C for 1 h.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Benchmarking of the Updated Resolved Resonance Region Evaluations of Copper

A new resolved resonance region (RRR) evaluation for the two naturally occurring isotopes of copper, {sup 63}Cu and {sup 65}Cu was performed at Oak Ridge National Laboratory (ORNL), and the benchmarking results based on the four highly enriched uranium (HEU), intermediate spectrum, copper-reflected Zeus experiments were presented in June 2014. Since then, two significant updates to the evaluations have been performed: first, the data for the experimental measurement of the capture cross section between 220 keV and 300 keV were renormalized and the resonance parameters were refitted. Second, the angular distribution of elastic scattering initially reported in point-wise form in File 4 of the ENDF file format with high fidelity was significantly reduced in size to allow for better computer storage. Twenty-seven criticality safety benchmarks from the International Criticality Safety Benchmark Evaluation Project (ICSBEP) were calculated using these updated resolved resonance region evaluations for the two isotopes of copper. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Amino Acid Immobilization of Copper Surface Diffusion on Cu(111)

Surface diffusion and molecular self-assembly are two critically important processes in chemistry and nature. Amino acids deposited on a Cu(111) surface driving a separation at the 2D limit between self-assembling molecules and diffusing copper atoms is reported. Since the self-assembling amino acids prefer non-planar, tridentate bonding with neighboring adatoms, they attach to and immobilize diffusing copper adatoms on the surface. This chemical interaction freezes out the copper diffusion causing the condensation of solid copper adatom islands on the surface. Such separation and immobilization are observed for eight different amino acids, suggesting the generality of this phenomenon beyond a single amino acid species. Furthermore, at elevated temperatures, a disruption of the prototypical Ostwald ripening of adatom islands is also observed. Here, these results provide fundamental insight into chiral molecular self-assembly and its interplay with metal atom surface diffusion.

36 MATERIALS SCIENCE↗