Copper Stabilizer Research Articles

Enhanced catalytic activity and stability of copper and nitrogen doped titania nanorod supported Pt electrocatalyst for oxygen reduction reaction in polymer electrolyte fuel cells

Copper and nitrogen doped TiO2 nanorod supported platinum with enhanced oxygen reduction and long-term durability in PEFCs.

Control of structure, stability and catechol oxidase activity of copper(ii) complexes by the denticity of tripodal platforms

The speciation and catecholase-like activity of trinuclear complexes can be fine tuned by the denticity of tripodal platforms.

Ligand Field and Counter Anion Effects on the Thermal Stability of Copper(II) Complexes of 1,2-Di(imino-4’-antipyrinyl)ethane and 4-N-(4’-antipyrylmethylidene) aminoantipyrine

A comparative thermolytic investigation on copper(II) complexes with two antipyrine Schiff base derivatives, namely 1,2-Di(imino-4’-antipyrinyl)ethane (GA) and 4-N-(4’-antipyrylmethylidene) aminoantipyrine (AA), with different counter anions like perchlorate,nitrate, chloride, and bromide has been done by thermogravimetric and derivative thermogravimetric analysis. The present investigation reveals that the counter anions and the ligand field play a big role on the thermal stability of the copper (II) complexes of both Schiff base derivatives. For the present complexes, the thermal decomposition mechanism has been investigated according to Satava, which follows a ‘random nucleation with one nucleus on each particle, i.e. the Mampel model’.

Zinc Complexes of Cyclodextrin-bearing 8-Hydroxyquinoline Ligands: A Comparative Study.

The mounting evidence supporting the role of metal ions in several diseases has turned metal-ion chelation therapy into a promising treatment strategy. The design of efficient metal-binding ligands requires in-depth knowledge of molecular structure and stability constants of the complexes formed. This paper presents an extensive overview on the stability of zinc(II) and copper(II) complexes of a series of cyclodextrin-8-hydroxyquinoline conjugates. In order to explain the differences observed in the stability constants between the metal complexes of the 6-functionalized and 3-functionalized cyclodextrin isomers, conformational analysis and DFT simulations were also performed. Molecular simulations allowed us to clarify the binding mode and to explain the differences in the stability constants of the metal complexes of these derivatives.

Stability of copper(II) complexes with nicotinate ion in water solutions of ethanol and dimethyl sulfoxide

The stability constants of copper(II) complexes with nicotinate ion in water–ethanol and water–dimethyl sulfoxide mixtures are determined potentiometrically at 25.0 ± 0.1°C at ionic strength of 0.25 (NaClO4). The stability of the copper(II) nicotinate complex significantly increases with ethanol content in the solution, thus making it possible to control the biologically important process by varying the solvent composition. The increase in DMSO concentration causes a less noticeable rise in stability, with its maximum observed at 0.1 dimethyl sulfoxide mole fractions. A comparative analysis of the findings and stability constants of Cu2+ complexes with pyridine-type ligands is carried out. The results are discussed using the solvation thermodynamics approach.

A Comparative Study of AC Transport and Eddy Current Losses for Coil Made of HTS Tapes Coated with Copper Stabilizer

In this work, the evaluation of AC loss of the pancake coils wound by HTS-coated conductors, by employing the finite element method in 2D, is presented. The transport current loss of the superconducting tape and the eddy current loss of the copper stabilizer as a function of the amplitude for four frequencies of the applied current are examined numerically by utilizing a newly developed calculation method based on the A − V formulation embedded in COMSOL Multiphysics software with an AC/DC module. The number of the coil turn is 10, and the radius is about 60 mm. The superconducting layer width and height in the simulations are 12 and 1 mm, respectively. The width and height of the copper layers are 12 and 80 mm, respectively. The critical current density of tapes is taken as 300 A.

Dispersion Stabilities of Multi-Layer Graphene-Coated Copper Prepared by Electrical Wire-Explosion Method

Dispersion Stabilities of Multi-Layer Graphene-Coated Copper Prepared by Electrical Wire-Explosion Method

Interfacial bonding enhancement of reel-to-reel selective electrodeposition of copper stabilizer on a multifilamentary second-generation high-temperature superconductor tape

A reel-to-reel copper selective electrodeposition process over a multifilamentary second-generation high-temperature superconductor (2G-HTS) has been demonstrated in our previous work. If the interfacial bonding between the deposited copper layer and the underlying silver overlayer is weak, it might lead to delamination in applications including magnets, motors and generators. In this study, two approaches have been used to improve the copper–silver bonding without the degradation of superconductor performance. The first approach is acidifying the electrolyte by adding sulfuric acid, by which the kinetics of copper electrodeposition is enhanced, resulting in finer microstructure at the copper–silver interface and thus, improved interfacial bonding strength. The second approach consists of blocking the electrolyte outflow at the entrance of the reel-to-reel electroplating cell, by which the occurrence of large copper seeds on the tape caused by the heavy turbulence flow is effectively prevented. With these two improvements together deployed in the process, the peeling strength between the copper and silver layers of the 2G-HTS tape has been improved from <0.3 N to >2 N in 90° peeling and from <0.5 N to >3.0 N in 180° peeling, without any degradation on the superconducting performance.

2G HTS wires made on 30 μm thick Hastelloy substrate

REBCO (RE = rare earth) based high temperature superconducting (HTS) wires are now being utilized for the development of electric and electromagnetic devices for various industrial, scientific and medical applications. In the last several years, the increasing efforts in using the so-called second generation (2G) HTS wires for some of the applications require a further increase in their engineering current density (Je). The applications are those typically related to high magnetic fields where the higher Je of a REBCO wire, in addition to its higher irreversibility fields and higher mechanical strength, is already a major advantage over other superconducting wires. An effective way to increase the Je is to decrease the total thickness of a wire, for which using a thinner substrate becomes an obvious and attractive approach. By using our IBAD-MOCVD (ion beam assisted deposition-metal organic chemical vapor deposition) technology we have successfully made 2G HTS wires using a Hastelloy® C276 substrate that is only 30 μm in thickness. By using this thinner substrate instead of the typical 50 μm thick substrate and with a same critical current (Ic), the Je of a wire can be increased by 30% to 45% depending on the copper stabilizer thickness. In this paper, we report the fabrication and characterization of the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate. It was shown that with the optimization in the processing protocol, the surface of the thinner Hastelloy® C276 substrate can be readily electropolished to the quality needed for the deposition of the buffer stack. Same in the architecture as that on the standard 50 μm thick substrate, the buffer stack made on the 30 μm thick substrate showed an in-plane texture with a Δϕ of around 6.7° in the LaMnO3 cap layer. Low-temperature in-field transport measurement results suggest that the wires on the thinner substrate had achieved equivalent superconducting performance, most importantly the Ic, as those on the 50 μm thick substrate. It is expected the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate, the thinnest and with the highest Je to date, will greatly benefit such applications as high field magnets and high current cables.

Structural Thermal Stability of Graphene Oxide-Doped Copper–Cobalt Oxide Coatings as a Solar Selective Surface

3d transition metal oxides based thin film coatings such as copper-cobalt oxides exhibit high absorption in the visible region and low emittance in the infra-red to far-infra-red region of the solar spectrum which is favourable for use as potential selective surface materials in photothermal devices. These materials have the potential to minimize heating while increasing absorption in the operative spectrum range and therefore achieve higher solar selectivity. A series of mixed copper-cobalt metal spinel oxides (CuxCoyOz) doped with graphene oxide thin films were deposited on commercial grade aluminium substrates using a sol–gel dip-coating technique at an annealing temperature of 500 °C in air for 1 h. Characterizations of the synthesized films were carried out by high temperature synchrotron radiation X-ray Diffraction (SR-XRD), UV-Vis, Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron microscopy (XPS) techniques. High thermal stability of coatings with multiple phases, binary and ternary metal oxides, was defined through SR-XRD study. FTIR analysis shows moderate (<80%) to high (up to 99%) reflectance in the infra-red region while the UV-Vis investigations demonstrate that, in the visible region, solar absorption increases gradually (up to 95%) with the addition of graphene oxide to the CuxCoyOz coatings. With the incorporation of 1.5 wt% of graphene oxide to the copper-cobalt oxide coatings, a high solar selectivity of 29.01 (the ratio of the average solar absorptance in visible and the average thermal emittance in infra-red to far infra-red region; α/e) was achieved.

Improved thermal stability and reliability of Cu film electrode induced by bias magnetron sputtering

The performance degradation of the thin-film electrodes has remained a challenge for the whole performance of micro-devices. Here, we introduce substrate bias voltage (SBV) in magnetron sputtering technique to improve the thermal stability and reliability of copper (Cu) electrode. The effects of the SBV on the stability and reliability of Cu film electrodes were investigated by scanning electron microscopy and thermal shock. Unstable electric performance is suppressed, and the interface bonding strength between the film and substrate is obviously improved by applying SBV. In addition, this work provides a facile way to achieve high reliability and thermal stability for Cu electrodes used in various thin-film devices.

Composition and stability of copper(II), nickel(II), and cobalt(II) complexes with mono- and bis(2-carboxy)-2-pycolylamine

Complexation of N-(2-pyridyl)methyl-3-aminopropionic (HL1) and N-(2-pyridyl)methyliminodipropionic (H2L2) acids with copper(II), nickel(II), and cobalt(II) ions is studied. The composition of complexes is determined using the Starik–Barbanel relative yield method. The acid dissociation constants of HL1 and H2L2 are determined potentiometrically; the stability constants of HL1 and H2L2 complexes with metal ions are calculated.

Promotion Effect of Adding Cr/Al/Fe to Cu/ZnO on the Stability of Hydrogen Produciton Catalyst for Dimethyl Ether Steam Reforming

Steam reforming (SR) of dimethyl ether (DME) is one of the promising ways to produce hydrogen for fuel cells (FCs) [1]. DME is harmless with a high H/C ratio, handling DME is easy because it is liquefied under ca. 6 atm and conventional facilities providing LPG can be used due to the similarity of DME to LPG.Coppper based materials were considered as good catalyst for DME SR [2]. However the durability of copper based catalysts is not good because of the copper sintering as reaction running. There are two ways to improve the durability of copper based catalysts, one is to enhance the dispersion of copper or to improve the thermal stability of copper by forming a spinel oxide or alloy [3]. γ-Al2O3 was used as support. The Cu/ZnO/γ-Al2O3, Cu/ZnO/Cr2O3/γ-Al2O3 and Cu/ZnO/Fe2O3/γ-Al2O3 catalysts were prepared by impregnation method. The nitrates were impregnated into support for 6 h, then dried at 323 K for 12 h, calcined at 823 K for 4h. The DME SR was carried out with a fixed bed flow reactor under atmospheric pressure using 1 g of catalyst at 773 K. After the catalyst was reduced by 12 v% H2/Ar at 503 K for 3 h, the mixed gas of DME and N2 (20 v%) were fed into the reactor with GHSV=500 ml/(g·h), the water was pumped into the reactor though a 473 K heater. The H/C ratio was 3. The catalysts were characterized by means of XRD, TPR, SEM, and BET. Steam reforming of DME was carried out at 773 K over Cu/ZnO/γ-Al2O3, Cu/ZnO/Cr2O3/γ-Al2O3 and Cu/ZnO/Fe2O3/γ-Al2O3 catalysts. The conversion of DME and the hydrogen yield reached 100% and 87% respectively for Cu/ZnO/γ-Al2O3 at the initial stage. The durability of this catalyst exhibted degradation. After running for 97 h, the hydrogen yield decreased to less than 60%. The reason for this degradation was supposed to be the sintering of copper, therefore, a metal oxide with better thermal stability was added into the catalyst to prevent the sintering of copper. The time-on-stream results indicate that the addtion of Cr2O3 or Fe2O3 can improve the durability of the catalyst for DME SR significantly. After running for 100 h, the hydrogen yield was kept at 84% and 85%, respectively. Figure 1 is the time-on-stream result of DME conversion over Cu/ZnO/ Cr2O3. Figure 1 is the time-on-stream result of DME conversion over Cu/ZnO/ Fe2O3. The mechanism of the improvement of the durability of catalysts were further investigated by XRD, SEM, BET and TPR. Figure 1

Redox Activity of Copper(II) Complexes with NSFRY Pentapeptide and Its Analogues.

The influence of cation-π interactions on the electrochemical properties of copper(II) complexes with synthesized pentapeptide C-terminal fragment of Atrial Natriuretic Factor (ANF) hormone was studied in this work. Molecular modeling performed for Cu(II)-NSFRY-NH2 complex indicated that the cation-π interactions between Tyr and Cu(II), and also between Phe-Arg led to specific conformation defined as peptide box, in which the metal cation is isolated from the solvent by peptide ligand. Voltammetry experiments enabled to compare the redox properties and stability of copper(II) complexes with NSFRY-NH2 and its analogues (namely: NSFRA-NH2, NSFRF-NH2, NSAAY-NH2, NSAAA-NH2, AAAAA-NH2) as well as to evaluate the contribution of individual amino acid residues to these properties. The obtained results led to the conclusion, that cation-π interactions play a crucial role in the effective stabilization of copper(II) complexes with the fragments of ANF peptide hormone and therefore could control the redox processes in other metalloproteins.

Stress responses and specific metal exclusion on mine soils based on germination and growth studies by Australian golden wattle

We reported the Australian golden wattle as a copper stabilizer in abandoned copper mine soils earlier. Here we investigate to confirm this plant’s suitability to grow on metal contaminated mine soils based on stress indication. The seeds of Acacia pycnantha collected from mining area were germinated after heat and no heat treatment on two types of irrigation. The daily irrigated and heat treated seeds gave up to 85% germination on sandy soil. The A. pycnantha was grown under greenhouse condition in six different soils collected from abandoned copper mine at Kapunda in South Australia. Among the six soil samples, soil-1 with the highest copper concentration produced 2.05mmolg−1 tissue of proline. Proline expression was prominent in more saline soils (1, 5 and 6) having electrical conductivity (EC) 1184, 1364 and 1256μS, respectively. Chlorophyll a, b and carotenoid levels in plants showed a gradually decreasing trend in all the soils as experiment progressed. The plants grown on soil sample-1, containing 4083±103mgkg−1 of copper resulted in 18±2mgkg−1 accumulation in its leaf. The calcium accumulation was significant up to 11648±1209mgkg−1 in leaf. Although pore water samples showed higher Cu concentration in soils, an increased mobility of arsenic and lead was observed in all the soil samples. Our experiment points out the need for proper monitoring of revegetation processes to avoid revegetation and reclamation failure.

Quench Protection Studies of the 11-T Nb3Sn Dipole for the LHC Upgrade

The planned upgrade of the LHC collimation system foresees additional collimators to be installed in the dispersion suppressor areas. Fermilab and CERN are developing an 11-T Nb3Sn dipole to replace some 8.33-T 15-m-long Nb-Ti LHC main dipoles providing longitudinal space for the collimators. In case of a quench, the large stored energy and the low copper stabilizer fraction make the protection of the 11-T Nb3Sn dipoles challenging. This paper presents the results of quench protection analysis, including quench protection heater design and efficiency, quench propagation, and coil heating. The numerical results are compared with the experimental data from the 2-m-long Nb3Sn dipole models. The validated model is used to predict the current decay and hot spot temperature under operating conditions in the LHC, and the presently foreseen magnet protection scheme is discussed.

Effect of Resistive Metal Cladding of HTS Tape on the Characteristic of No-Insulation Coil

This paper presents experimental and theoretical studies of the no-insulation (NI) winding method of second-generation high-temperature superconducting (HTS) wire. We compared two single pancake coils wound by two different HTS wires. One pancake coil is made of a normal HTS wire with an electroplated copper stabilizer. The other pancake coil is made of the same HTS wire with the only difference in an additional outermost layer made of stainless steel. We employed an equivalent circuit model to evaluate our experimental results. We tested both coils by the same simple operating procedure consisting of two steps: first, ramping up of current from zero to holding current (IH) and second, keeping the IH at minimum 500 s. We also tested the stability of the coil wound by an HTS wire with an additional layer of stainless steel by applying a current exceeding a critical current of the coil. We observed a charging time of the metal-cladding HTS coil reduced to a quarter of copper-electroplated HTS coil.

Influence of turn-to-turn resistivity and coil geometrical size on charging characteristics of no-electrical-insulation REBCO pancake coils

High temperature superconductor (HTS) no-electrical-insulation (NEI) coils demonstrate great advantages in thermal stability and self-protection features. However, an intrinsic delay is observed in the charging process and as a result there maybe a possible settle-out problem. It becomes more critical for large HTS coils with more turns, such as the magnets for the accelerator system and DC induction heater applications. This paper presents detailed studies on the charging characteristics of NEI coils. Firstly, two different no-electrical-insulation coils are wound: the first is directly wound using only REBCO tapes with brass lamination, which is called a no-insulation (NI) coil. The other one is co-wound with stainless steel (SS) strips and REBCO tapes whose copper stabilizer is electroplated, which is called a metallic insulation (MI) coil. Fast discharging tests are performed on the two coils and their equivalent turn-to-turn resistivity is calculated. A similar discharging delay is observed on both coils, but the turn-to-turn resistivity of the SS co-wound coil is much higher than that of the first coil. Then the resistivity data is directly applied to an equivalent circuit network model which is developed to predict the charging behaviours. The model calculates coil voltage, currents along the azimuthal and radial directions, as well as the induced magnetic field. A practical charging time is defined to characterize the field ramping process considering the charging delay between field ramping and current charging. The charging behaviours are extensively analyzed and compared in terms of three primary factors: equivalent turn-to-turn resistivity, coil size and ramping rate. The results show that the charging time increases dramatically with the coil size and may be too long to be practical for large-scale applications using HTS coils with low turn-to-turn resistivity. Increasing the turn-to-turn resistivity enables one to accelerate the charging process effectively. Therefore, the SS co-wound coil with higher turn-to-turn resistivity shows a much shorter charging time, which indicates that it may be more suitable for large-scale HTS magnets.

Long-term stability of Cu surface nanotips

Sharp nanoscale tips on the metal surfaces of electrodes enhance locally applied electric fields. Strongly enhanced electric fields trigger electron field emission and atom evaporation from the apexes of nanotips. Together, these processes may explain electric discharges in the form of small local arcs observed near metal surfaces in the presence of electric fields, even in ultra-high vacuum conditions. In the present work, we investigate the stability of nanoscale tips by means of computer simulations of surface diffusion processes on copper, the main material used in high-voltage electronics. We study the stability and lifetime of thin copper (Cu) surface nanotips at different temperatures in terms of diffusion processes. For this purpose we have developed a surface kinetic Monte Carlo (KMC) model where the jump processes are described by tabulated precalculated energy barriers. We show that tall surface features with high aspect ratios can be fairly stable at room temperature. However, the stability was found to depend strongly on the temperature: 13 nm nanotips with the major axes in the crystallographic directions were found to flatten down to half of the original height in less than 100 ns at temperatures close to the melting point, whereas no significant change in the height of these nanotips was observed after 10 at room temperature. Moreover, the nanotips built up along the crystallographic directions were found to be significantly more stable than those oriented in the or crystallographic directions. The proposed KMC model has been found to be well-suited for simulating atomic surface processes and was validated against molecular dynamics simulation results via the comparison of the flattening times obtained by both methods. We also note that the KMC simulations were two orders of magnitude computationally faster than the corresponding molecular dynamics calculations.

High-Efficient Copper Shunt Deposition Technology on REBCO Tape Surfaces

For low-ohmic electrical applications of REBCO- coated conductors (CCs), a copper stabilizer with thickness of at least 20-30 μm is indispensable. The electroplating process investigated herein was developed in the last ten years. We investigated and proposed Cu pulse plating on a CC surface protecting the tape, preventing sharp edges and facilitate winding work. With an optimized chemistry of the copper sulfate CuSO 4 + H 2 SO 4 solution, we deposited a shiny, ductile, and nonporous copper layer. Due to cell-specific current load-controlled pulse plating technology, both Ni-based Hastelloy and NiW substrates could be plated with a current density of up to 200 mA/cm 2 . It reveals that pulse- controlled electrodeposition in a reel-to-reel technique brings the CC production to perfection. The nonvacuum copper plating technique is targeting a production speed of 100 m/h. The method meets the urgent need for simplified conductors and a reduced cost/performance ratio. We report about the electric and chemical parameters of a robust reel-to-reel facility. An improvement of the deposition rate and an increase of the Cu deposition speed up to 100 m/h is discussed.