Introduction Of CuO Research Articles

Fabrication of boron nitride/copper oxide@multi-walled carbon nanotubes composites for enhancing heat transfer and photothermal conversion of phase change materials

To realize the efficient storage and conversion of solar energy by phase change materials (PCMs), low photothermal conversion efficiency and poor heat transfer performance remain great challenges. Herein, polyethylene glycol (PEG)-based composite PCMs with excellent photothermal conversion performance and exceptional thermal management capability were obtained by using boron nitride/copper oxide@multi-walled carbon nanotubes (BN/CuO@MWCNTs) as the thermal conductive and photothermal conversion enhancement fillers. The results indicate that owing to the bridging effect, the introduction of CuO and MWCNTs on the BN surface can construct additional heat transfer paths, resulting in a high thermal conductivity of up to 2.35 W/(m·K) for the as-prepared PEG/BN/CuO@MWCNTs composite, which is about 9-folds enhancement than pristine PEG. Simultaneously, the supercooling degree of PEG in PEG/BN/CuO@MWCNTs is effectively suppressed due to the synergistic nucleation effect of BN, CuO and MWCNTs. Additionally, the PEG/BN/CuO@MWCNTs composites not only exhibit a high latent-heat capacity of 154.5 J/g and a high photothermal conversion efficiency of 92.2 %, but also show favorable shape stability and durable reliability. This work offers a workable solution for the synergistic enhancement of photothermal conversion and thermal management, which can effectively promote the practical application in solar energy conversion and storage.

Thermal Sintering Matchability between Low‐Temperature Cofired Ceramic Substrate and Silver Pastes and the Effect of CuO on Silver Diffusion Inhibition

Low‐temperature cofired ceramic (LTCC) materials are a promising material for heat dissipation substrates due to their excellent thermal conductivity and thermal expansion coefficient similar to that of silicon. However, the difficulties in surface metallization techniques limit its application. This work uses Bi–B–Si–Zn–Al glass/ceramic composite as the substrate and Bi–B–Si–Zn–Al glass powder as the inorganic binder for silver pastes. The silver thick film with a glass content of 3 wt% is sintered at 800 °C for 30 min, and the samples have excellent electrical conductivity (surface square resistance of 0.29 mΩ £−1) and mechanical properties (interface bonding force of 17.56 MPa). In addition, the introduction of CuO into the glass phase can inhibit the silver diffusion phenomenon during the sintering process and improve the conductive performance of the material. The results are beneficial for the preparation and application stability of LTCC devices.

Hierarchical Design of CuO/Nickel-Cobalt-Sulfide Electrode by a Facile Two-Step Potentiostatic Deposition.

Herein, a scalable electrodeposition strategy is proposed to achieve hierarchical CuO/nickel-cobalt-sulfide (NCS) electrodes using two-step potentiostatic deposition followed by high-temperature calcination. The introduction of CuO provides support for the further deposition of NSC to ensure a high load of active electrode materials, thus generating more abundant active electrochemical sites. Meanwhile, dense deposited NSC nanosheets are connected to each other to form many chambers. Such a hierarchical electrode prompts a smooth and orderly transmission channel for electron transport, and reserves space for possible volume expansion during the electrochemical test process. As a result, the CuO/NCS electrode exhibits superior specific capacitance (Cs) of 4.26 F cm-2 at 20 mA cm-2 and remarkable coulombic efficiency of 96.37%. Furthermore, the cycle stability of the CuO/NCS electrode remains at 83.05% within 5000 cycles. The multistep electrodeposition strategy provides a basis and reference for the rational design of hierarchical electrodes to be applied in the field of energy storage.

Loading CuO on the surface of MgO with low-coordination basic O2− sites for effective enhanced CO2 capture and photothermal synergistic catalytic reduction of CO2 to ethanol

The higher capacity of CO2 adsorption on the surface of magnesium oxide (MgO) with low-coordination O2− sites would effectively enhance the catalytic reduction of CO2. Herein, a series of copper oxide (CuO) and MgO composites with different mass ratios have been prepared by hydrothermal method and used for photothermal synergistic catalytic reduction of CO2 to ethanol. The catalyst with CuO mass ratio of 1.6% shows the best yield (15.17 μmol·g−1·h−1) under 3 h Xenon lamp illumination. The improved performance is attributable to the loose nano-sheet structure, uniform dispersion of active sites, the increased specific surface area, medium-strengthbasicity, the high separation efficiency of electrons and holes, and the formation of Mg−O−Cu species. The synthesized CuO and MgO composites with loose nano-sheet structure facilitate the diffusion of reactants CO2, so an excellent CO2 adsorption performance can be obtained. Meanwhile, the introduction of CuO in the form of bivalence provides higher specific surface area and porosity, thus obtaining more active sites. Moreimportantly, the Mg−O−Cu species make the donation of electrons from MgO to CO2 easier, resulting in the breaking of the old Mg-O bond and the formation of C—O bond, thus promoting the adsorption and conversion of CO2 to ethanol.

In Tandem Control of La-Doping and CuO-Heterojunction on SrTiO3 Perovskite by Double-Nozzle Flame Spray Pyrolysis: Selective H2 vs. CH4 Photocatalytic Production from H2O/CH3OH.

ABO3 perovskites offer versatile photoactive nano-templates that can be optimized towards specific technologies, either by means of doping or via heterojunction engineering. SrTiO3 is a well-studied perovskite photocatalyst, with a highly reducing conduction-band edge. Herein we present a Double-Nozzle Flame Spray Pyrolysis (DN-FSP) technology for the synthesis of high crystallinity SrTiO3 nanoparticles with controlled La-doping in tandem with SrTiO3/CuO-heterojunction formation. So-produced La:SrTiO3/CuO nanocatalysts were optimized for photocatalysis of H2O/CH3OH mixtures by varying the La-doping level in the range from 0.25 to 0.9%. We find that, in absence of CuO, the 0.9La:SrTiO3 material achieved maximal efficient photocatalytic H2 production, i.e., 12 mmol g-1 h-1. Introduction of CuO on La:SrTiO3 enhanced selective production of methane CH4. The optimized 0.25La:SrTiO3/0.5%CuO catalyst achieved photocatalytic CH4 production of 1.5 mmol g-1 h-1. Based on XRD, XRF, XPS, BET, and UV-Vis/DRS data, we discuss the photophysical basis of these trends and attribute them to the effect of La atoms in the SrTiO3 lattice regarding the H2-production, plus the effect of interfacial CuO on the promotion of CH4 production. Technology-wise this work is among the first to exemplify the potential of DN-FSP for scalable production of complex nanomaterials such as La:SrTiO3/CuO with a diligent control of doping and heterojunction in a single-step synthesis.

A room-temperature NO2 sensor based on Ti3C2TX MXene modified with sphere-like CuO

In this paper, the Ti3C2Tx/CuO nanocomposites were successfully prepared by an environment-friendly and simple hydrothermal method. The synthetics are evaluated using a series of characterization techniques, such as XRD, SEM, TEM, XPS, FTIR, UV–vis, and BET techniques. The results show that Ti3C2Tx/CuO nanocomposites are mesoporous and have a higher specific surface area than Ti3C2Tx, confirming the presence of more gas adsorption/diffusion regions. Furthermore, the Ti3C2Tx with the introduction of CuO has rich oxygen vacancies and adsorbed oxygen. In particular, the response of Ti3C2Tx/CuO sensor (56.99%) is 5 times higher than that of Ti3C2Tx (11.17%) sensor to 50 ppm NO2 at room temperature (RT). Especially, the Ti3C2Tx/CuO sensor exhibits ultra-fast response/recovery time (16.6/31.3 s to 20 ppm NO2), great reversibility, outstanding selectivity to NO2, and desirable long-term stability (over 40 days). The enhanced gas sensing performance may be attributed to the formation of hybrid heterojunctions between CuO and Ti3C2Tx that provide carrier migration channels to hasten the redox reaction. At the same time, Ti3C2Tx/CuO possesses more oxygen vacancies and adsorbed oxygen than Ti3C2Tx, which will reduce the required energy for gas adsorption to further enhance the gas sensing performance. Hopefully, the above improved gas sensing performance indicators modified with CuO are expected to become the advantage of constructing Ti3C2Tx-based sensor, which will be put into commercial NO2 detection in the future.

Effect of intergrowth and coexistence CuO-CeO2 catalyst by grinding method application in the catalytic reduction of NOx by CO

Abstract Heterogeneous symbiosis and coexistence CuO-CeO2 catalyst is prepared by simple grinding method to explore the symbiosis effect and the influence of different ratios of CeO2 and CuO on the catalyst structure and catalytic performance. All samples were characterized using XRD, TEM, N2 adsorption-desorption, LRS, H2-TPR, XPS, in situ FT-IR, the catalytic performance of the catalyst is evaluated by the CO + NO model reaction. Among them, Cu1Ce2 catalyst shows excellent catalytic performance, and testing for SO2 or/and H2O resistance. In the catalytic reaction, Cu+ in the catalyst plays an important role, and it is related to the active site where the NO molecule dissociates. Combining all the characterization results, it is shown that the introduction of CuO in the two-phase coexistence catalyst can effectively improve the oxygen vacancy content and the catalytic activity. Simultaneously, we proposed a possible mechanism for two-phase coexisting catalysts of reduction NO by CO to further understand the catalytic process.

3D Urchin-Like CuO Modified W18O49 Nanostructures for Promoted Photocatalytic Hydrogen Evolution under Visible Light Irradiation.

Photocatalytic hydrogen evolution is a promising “green chemistry” route driven by sunlight for the direct water splitting into value-added hydrogen energy. Herein, with the object of exploring the effect of CuO loading on W18O49 photocatalytic activity, a 3D Urchin-like CuO modified W18O49 (CuO/W18O49) microspheres with different CuO loadings were synthesized via thermochemical precipitation combined with solvent-thermal method. The obtained CuO/W18O49 microspheres were analyzed by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL), etc. The results infer that the urchin-like 3D morphology with a high surface area and abundant 1D nanowires promotes electron transfer, the introduction of CuO further increases the number of active sites, thereby ensuring fast interfacial charge transfer to improve photocatalytic performance. During photocatalytic H2 evolution from water splitting, 5 wt.% CuO/W18O49 shows the optimal performance, the H2 yield is almost 3.22 times that of the undoped counterparts. This work presents that oxygen-vacancy-rich heterojunction nanocomposites can be used as a new strategy to design materials with high photocatalytic activity.

Local structure and conductivity of highly conductive vanadate glasses containing different metal oxides

Heat treatment of 20BaO·xMmOn·(10−x)Fe2O3·70V2O5 glasses containing different metal oxides (MmOn), such as Fe2O3, Al2O3, MnO2, CuO, Cu2O, ZnO, Ga2O3, GeO2, MoO3, SnO2 and WO3, was accompanied by a remarkable decrease in DC-resistivity (ρ) at room temperature from the order of MΩ cm to Ω cm. N-type semiconductor model could be successfully applied to discuss the conduction mechanism. Introduction of CuO into network former (NWF) sites caused a remarkable change of ρ from 2.6 × 105 to 3.1 Ω cm when annealed at 450 °C for 30 min. Activation energy for conduction (Ea) decreased from 0.16 to 0.10 eV, suggesting an increased carrier density in the conduction band. Diffuse reflectance spectra of this glass showed a decrease in the bandgap energy (Eg) from 2.41 to 2.14 eV. Introduction of ZnO into network modifier (NWM) sites resulted in a remarkable decrease in ρ from 4.0 × 105 to 4.8 Ω cm after annealing at 450 °C for 30 min, together with a decrease in Ea from 0.23 to 0.14 eV. Diffuse reflectance spectra showed a decrease in Eg from 2.39 to 2.11 eV. These results prove that heat treatment of vanadate glass causes structural relaxation and concordant decrease in Ea and Eg which are responsible for the remarkable increase in the high conductivity.

Influence of Copper Oxide and Silver Nanoparticles on Microclonal Sprouts of Downy Birch (Betula pubescens Ehrh.)

The effects of using nanoparticles of copper oxide (5–40 nm) and silver (10–30 nm) in the clonal micropropagation of downy birch were studied. The addition of nanoparticles to WPM medium (Woody plant medium) at the stage of introducing explants into culture in vitro helps reduce the infection of explants by 15–25%, as well as increase their morphogenic potential. The use of colloidal solutions of CuO and Ag nanoparticles when transferring birch microplants to greenhouses reduces the number of plants infected by phytopathogens increases their survival rate by 25%. A decrease in the overall infectious load and an increase in the adaptive potential due to nanoparticles improves the main growth and development indicators of downy birch plants. At the stages of multiplication and rooting of birch microclones, the introduction of CuO and Ag nanoparticles into WPM contributed to decreased viability; deterioration in the appearance, development of shoots and leaves; and a decrease in the microclone multiplication coefficient. No positive effect of the introduction of nanoparticles on the number of rooted birch microplants in vitro was found. Note that under the action of CuO nanoparticles, in contrast to Ag nanoparticles, the birch root system became more branched, with a large number of lateral roots. The results can be applied when using CuO and Ag nanoparticles in the biotechnology of plant clonal micropropagation.

Synthesis and Characterization of CuMnOx-Bentonite as Efficient Catalyst for Oxidation of m-xylene

Catalytic oxidation of organic volatile compounds (VOCs) is considered superior to conventional methods because very low concentration of VOCs can also be oxidized and removed at low temperatures without consumption of addditional fuel and introduction of NOx compounds into the environment. Herein, the synthesis of MnO2 nanoparticles on bentonite (Bent) support in the presence of CuO for catalytic oxidation of m-xylene is reported. The synthesized materials were analyzed with FT-IR, XRD, and TEM analysis for structural and morphological characterization. XRD and TEM analysis indicated the formation of δ-MnO2 with sheet structure on Bent surface. Temperature-programmed reduction (H2-TPR) of hydrogen was used to investigate catalytic performance of δ-MnO2 towards oxidation of m-xylene at different temperatures. The catalytic activity was strongly dependent on the δ-MnO2 content in the synthesized material. 100 % oxidation of m-xylene with observed with 10% Mn content at temperature below than 325 oC. Intersetingly introduction of CuO greatly improved the catalytic activity of Mn-Bent materials. The presence of Cu in Mn-Bent has greatly reduced the temperature for complete oxidation of m-xylene. In this case100% conversion of m-xylene was observed at 250 oC.

Heterogeneous catalytic ozonation of oxalic acid with an effective catalyst based on copper oxide modified g-C3N4

Various amounts of copper oxide (CuO) modified graphitic carbon nitride (g-C3N4) denoted as CuO-CNx composites were successfully fabricated via a reflux condensation method and used as efficient ozonation catalysts for oxalic acid (OA) degradation in aqueous solution. The BET, FT-IR, HRSEM, TEM, XPS, etc. characterizations revealed the chemical composition, bond structure and morphologies of as-prepared CuO-CNx composites. The results indicated that the introduction of CuO into g-C3N4 relying on the chemical interaction rather than simple physical mixture. Moreover, the increased active sites and the intense chemical bonds could play important roles in improving the catalytic ozonation performances of CuO-CNx composites. In this study, the practical applications of catalysts at different conditions were also investigated. When the mass ratio of CuO/g-C3N4 was 10, the CuO-CN10 composite exhibited superior catalytic ozonation activity with 97.9% OA removal efficiency after 30 min at pH 5.0. Meanwhile, the CuO-CN10 showed excellent stability and reusability for contaminant degradation during multiple consecutive cycles. Furthermore, hydroxyl radical and superoxide radical as the major reactive radicals were identified and the catalytic mechanism for OA degradation improvement was also elucidated. Overall, this work would provide an efficient and eco-friendly catalyst for water treatment as well as a new idea for future environmental purification.

Nanorods to hexagonal nanosheets of CuO-doped manganese oxide nanostructures for higher electrochemical supercapacitor performance

In this work, the extraordinary properties of CuO addition on the morphology and supercapacitive performance of Mn2O3 electrodes were demonstrated. Concisely, CuO/Mn2O3 thin films were prepared by an easy and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The prepared thin films were characterized by various sophisticated physiochemical systems. The results demonstrated formation of Mn2O3 thin films with noteworthy morphological alteration upon introduction of CuO. Furthermore, a significant effect of CuO introduction was observed on the electrocatalytic properties of the nanostructured Mn2O3 electrodes. At 3% CuO doping, the Mn2O3 electrodes displayed the maximum specific capacitance owing to formation of nanoplate-like structures. The enhanced specific capacitance attained for 3% CuO doping in the Mn2O3 electrode was 500 F/g at 5 mV/s in a 3 M KOH electrolyte. All results confirmed the plausible potential of the CuO/Mn2O3 electrode for supercapacitor applications.

Study on the effect of copper ion doping in zinc oxide nanomaterials for photocatalytic applications

Abstract ZnO has been reported to be a promising photocatalytic material for dye degradation. But the quick recombination of the photo-generated charge carriers and low stability due to photo corrosion has been a major drawback of these material. In addition to this, the large band gap of ZnO makes it inefficient for the utilization of Sun light, specially in the visible region. In order to overcome these demerits, various methods like modification of morphology, doping, forming composite, etc. have been adopted. This work reports the effect of Cu ion doping in ZnO nanomaterials on its photocatalytic characteristics. Pure and Cu ion doped ZnO (Cu:ZnO) nanopowders with varying Cu ion content from 0 to 20 wt% had been synthesized by hydrothermal method. Single phase of wurtzite hexagonal ZnO was formed up to 10 wt% of Cu doping into the ZnO, beyond which the samples have become biphasic with the introduction of CuO as secondary phase, showing that 10 wt% was the solubility limit of Cu in ZnO lattice. Average crystallite size calculated by Scherrer formula was in the range from 21.9 to 39.0 nm. Strain in pure and Cu:ZnO was calculated by Williamson and Hall analysis. Optical absorption analysis showed that the band gap had decreased from 3.25 to 3.11 eV with increasing Cu content. Near-band edge (NBE) and a broad yellow emission bands with the maxima respectively at 382 and 561 nm were observed in the photoluminescence spectra of Cu:ZnO. The photocatalytic activity of these samples was investigated by the oxidation of methyl orange dye under UV light as well as under Sun light irradiation. The results indicated that the photocatalytic degradation of the MO solution under UV irradiation shows 83.8% for ZnO whereas the 1% Cu:ZnO have degraded the best with 99.5% of MO under Sun light irradiation.

Preparation and electrocatalytic performance of nanoporous Pd/Sn and Pd/Sn-CuO composite catalysts

Nanoporous (np) Pdx/Sn15-x (x = 1, 5, 8, 13) and Pd5/Sn10-CuO-y (y = 1, 2, 3, 4) electrocatalysts are synthesized via a one-step dealloying method in NaOH solution. All of the as-prepared catalysts exhibit a bicontinuous nanoporous structure. The np-Pd5/Sn10 catalyst exhibits the best electrocatalytic performance among the np-Pd/Sn catalysts. Due to the bifunctional effects between Sn and Pd, the catalyst with suitable Pd/Sn atomic ratio can effectively expose Pd active sites during the methanol oxidation process. The peak current density of np-Pd5/Sn10 catalysts is much higher than that of np-Pd catalyst. The introduction of CuO in np-Pd/Sn catalysts could significantly improve the long-term stability for methanol electro-oxidation. The peak current density of np-Pd5/Sn10-CuO-2 is about 2 times higher than that of np-Pd5/Sn10 catalyst after the stability test.

Pt-Embedded CuO x-CeO2 Multicore-Shell Composites: Interfacial Redox Reaction-Directed Synthesis and Composition-Dependent Performance for CO Oxidation.

Exploring the state-of-the-art heterogeneous catalysts has been a general concern for sustainable and clean energy. Here, Pt-embedded CuO x-CeO2 multicore-shell (Pt/CuO x-CeO2 MS) composites are fabricated at room temperature via a one-pot and template-free procedure for catalyzing CO oxidation, a classical probe reaction, showing a volcano-shaped relationship between the composition and catalytic activity. We experimentally unravel that the Pt/CuO x-CeO2 MS composites are derived from an interfacial autoredox process, where Pt nanoparticles (NPs) are in situ encapsulated by self-assembled ceria nanospheres with CuO x clusters adhered through deposition/precipitation-calcination process. Only Cu-O and Pt-Pt coordination structures are determined for CuO x clusters and Pt NPs in Pt/CuO x-CeO2 MS, respectively. Importantly, the close vicinity between Pt and CeO2 benefits to more oxygen vacancies in CeO2 counterparts and results in thin oxide layers on Pt NPs. Meanwhile, the introduction of CuO x clusters is crucial for triggering synergistic catalysis, which leads to high resistance to aggregation of Pt NPs and improvement of catalytic performance. In CO oxidation reaction, both Ptδ+-CO and Cu+-CO can act as active sites during CO adsorption and activation. Nonetheless, redundant content of Pt or Cu will induce a strongly bound Pt-O-Ce or Cu-[O x]-Ce structures in air-calcinated Pt/CuO x-CeO2 MS composites, respectively, which are both deleterious to catalytic reactivity. As a result, the composition-dependent catalytic activity and superior durability of Pt/CuO x-CeO2 MS composites toward CO oxidation reaction are achieved. This work should be instructive for fabricating desirable multicomponent catalysts composed of noble metal and bimetallic oxide composites for diverse heterogeneous catalysis.

Enhanced photocatalytic decomposition of VOCs by visible-driven photocatalyst combined Cu-TiO2 and activated carbon fiber

Abstract Volatile organic compounds (VOCs) threaten the environment and human health, as many of them are highly toxic and carcinogenic. For this reason, a larger of VOCs control techniques have developed. This study, Cu-TiO2 combine with activated carbon fiber (Cu-Ti/ACF) was prepared and used as visible light-driven photocatalyst material for removal of toxic VOCs (benzene and toluene) in aqueous solution. The Cu-Ti/ACF was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), specific surface area (BET), X-ray photoelectron spectroscopy (XPS) and UV–vis spectrophotometer. The adsorption and photocatalytic degradation of benzene and toluene was test under different condition including the solution pH (4.0–10), catalyst dose (0.01 to 0.5 g), reaction time (0–180 min) and initial concentration ranged of 10–200 mg/L. Under the visible light, the degradation efficiencies of benzene and toluene were up to 81.2 and 97.8%, respectively. Reusability of Cu-Ti/ACF was tested and the degradation efficiencies for benzene and toluene were not affected after three cycles. The introduction of CuO and TiO2 onto ACF effectively extended the spectral response of TiO2 to the visible light. On basis of these evidences, the mechanism degradation of benzene and toluene by Cu-Ti/ ACF was proposed. The paper suggests that the Cu-Ti/ACF has potential for degradation of benzene and toluene in aqueous solution.

Cycling‐ and heating‐induced evolution of piezoelectric and ferroelectric properties of CuO‐doped K0.5Na0.5NbO3 ceramic

AbstractFor accepter‐doped perovskite piezoelectric ceramics, macroscopic properties of the materials (eg, hardening, fatigue, and aging) are closely related to microscopic characteristics (eg, oxygen vacancies and defect dipoles). In this work, the relationship of macroscopic and microscopic characteristics in CuO‐doped K0.5Na0.5NbO3 (KNN) ceramic has been studied by subjecting the material to electric field cycling, quenching, heating, and consequently aging. The introduction of CuO in KNN generates and . The defect dipoles exhibit obviously the pinning effect on ferroelectric domains and thus induce a completely pinched/double P‐E loop and excellent hardening piezoelectricity of high Qm of 2235. With the destruction of short‐range symmetry uniformity between defect dipoles and ferroelectric dipoles induced by electric field cycling, quenching and heating, the ceramic can be depinned and softened. As a result, the depinned ceramic possesses an opened single ferroelectric hysteresis loop and the significantly decreasing Qm. A distinctive aging is observed in the depinned ceramic. This study provides deep insights into the evolution of electrical properties of accepter‐modified alkali niobate perovskite ceramics under electric field cycling, quenching, and heating.

Artificial Multilayers of REBaCuO/YBaCuO and YBCO/CuO(Y2O3) for High-Performance Long Tapes of Coated Conductors Derived by Metal Organic Solution Deposition

Thick superconducting multilayer architectures consisting of alternate superconducting and superconducting layers DyBCO/YBCO and alternate superconducting and insulating layers YBCO/CuO(Y 2 O 3 ) are developed on buffered Hastelloy tapes using a metal organic deposition process. It is revealed that multilayer intermittent structures for superconducting layers are effective to avoid the presence of microcracks that occur with increasing thickness, which are frequently observed in monolayer films of REBa 2 Cu 3 O 7-δ (REBCO, RE = Y, Gd, or other rare earth elements). This paper shows that the thicknesses of DyBCO/YBCO multilayer films can reach 2.8 μm with a homogeneous, dense and crack-free surface morphology. The out-plane FWHM of the YBCO (005) peaks and the critical current value reach 1.1° and 365 A/cm (77 K, self-field) for such a thick film consisting of DyBCO/YBCO multilayers. It is also revealed that the introduction of a CuO layer is effective to avoid the presence of a-axis grains and voids of the YBCO films, which are frequently observed in multilayer films. Note that the introduction of CuO shows little negative influence on the texture of multilayer structure, especially for the bottom CuO. However, the in-plane texture deteriorates seriously for Y 2 O 3 /YBCO/YBCO multilayer film. The critical current density of YBCO films with middle CuO and bottom CuO are 2.0 MA/cm 2 and 2.5 MA/cm 2 (77 K, self-field), respectively. The microstructure optimization including the texture, uniformity, crack, defect, and porosity in the multilayered films is probably the reason for the enhancement of superconducting performance.

Formation and effects of CuO nanoparticles on Ag/SnO2 electrical contact materials

The Ag/SnO2 contact materials modified by the in situ formed CuO nanoparticles were prepared through a self-assembly-precipitation method combined with powder metallurgy. The micro morphology and composition proportion of the Ag-CuO composite powders were investigated. The microstructures and physical properties of the prepared Ag-CuO/SnO2 materials were studied. After arc erosion, the surface morphology and element distributions of the Ag-CuO/SnO2 materials were characterized by Scanning Electron Microscopy (SEM) and Electron Probe Microanalysis (EPMA). The results showed that the CuO nanoparticles smaller than 10 nm were formed on the whole surface of Ag powder. The electrical conductivity of the Ag/SnO2 contact materials was significantly increased with the introduction of CuO, and the hardness, however, was slightly decreased, which could improve the workability. The formation of ultrafine CuO nanoparticles significantly improved the arc dispersion and arc erosion resistance of Ag/SnO2 materials. The aggregation of SnO2 particles in the erosion area was effectively suppressed.