CuO Content Research Articles

Polypropylene-based melt mixed composites with singlewalled carbon nanotubes for thermoelectric applications: Switching from p-type to n-type by the addition of polyethylene glycol

The thermoelectric properties of melt processed conductive nanocomposites consisting of an insulating polypropylene (PP) matrix filled with singlewalled carbon nanotubes (CNTs) and copper oxide (CuO) were evaluated. An easy and cheap route to switch p-type composites into n-type was developed by adding polyethylene glycol (PEG) during melt mixing. At the investigated CNT concentrations of 0.8 wt% and 2 wt% (each above the electrical percolation threshold of ∼0.1 wt%), and a fixed CuO content of 5 wt%, the PEG addition converted p-type composites (positive Seebeck coefficient (S)) into n-type (negative S). PEG was also found to improve the filler dispersion inside the matrix. Two composites were prepared: P-type polymer/CNT composites with high S (up to 45 μV/K), and n-type composites (with S up to −56 μV/K) through the addition of PEG. Two prototypes with 4 and 49 thermocouples of these p- and n-type composites were fabricated, and delivered an output voltage of 21 mV and 110 mV, respectively, at a temperature gradient of 70 K.

A multifunctional noble-metal-free catalyst of CuO/TiO2 hybrid nanofibers

Exploiting photocatalysts/catalysts with characteristics of low cost, high reactivity and easy recovery is of great significance for energy efficiency and environmental remediation. Herein, CuO/TiO2 hybrid nanofibers with different CuO contents were fabricated by a simple and low-cost method of electrospinning followed with calcinations in air. The hybrid nanofibers possess some distinct merits including mesoporous structure, extended light response range, and large TiO2/CuO interface. The CuO/TiO2 hybrid nanofibers showed improved photocatalytic activity for organic dye degradation under both simulated sunlight (UV–vis) and visible light (λ>420nm), compared with pure TiO2 nanofibers. Both processes exhibited humplike activity dependence upon CuO addition, with a peak at 1wt.%-CuO content under UV–vis light and a peak at 5wt.%-CuO content under visible light, respectively. The mechanism for the CuO-content dependent photocatalysis was discussed with the photoelectrochemical analysis in evidence. Moreover, the CuO/TiO2 hybrid nanofibers exhibited very high catalytic efficiency for the reduction of nitrophenols by sodium borohydride, and the apparent reaction rate constants ascended with the increased CuO content. The optimized CuO/TiO2 nanofibers are expected to act a highly efficient catalyst to replace the noble metals in this field. Therefore, this work demonstrated a convenient case for the exploitation of noble-metal-free catalysts with high efficiency, to meet the increasing demands of industrial applications at reduced costs.

Variation of the chemical composition of Pyrenean oak (Quercus pyrenaica Willd.) heartwood among different sites and its relationship with the soil chemical characteristics

This work presents the results of a study on the variation of the chemical composition of Pyrenean oak (Quercus pyrenaica Willd.) heartwood among different sites and its relationship with the soil chemical characteristics. The chemical characteristics of the heartwood are quantified in terms of proximate and ultimate analysis, calorific value and ash composition. Subsequently, the relationship between the wood chemical characteristics and the soil characteristics was also examined. The results showed no significant differences between the wood chemical characteristics from different sites. There are, however, significant differences between trees from the same site regarding the wood ash content, the calorific value and the contents of nitrogen and hydrogen. Strong correlations were observed between the heartwood ash contents of BaO, MnO, CuO and TiO2 and the soil nitrogen, phosphorous and potassium and the soil exchangeable base contents.

Fabrication and Characterizations of Aluminum-Doped Zinc Oxide (AZO): Cu2O/p-Si Photodiodes

In this paper, aluminum-doped zinc oxide (AZO):Cu2O/p-Si photodiode was fabricated based on simple solution process. The photodiodes were prepared using Zn1-xAlxO:Cu2O thin films grown on p-Si substrates. The photoresponse properties of the p-Si/AZO:Cu2O/Al photodiodes were investigated by current-voltage and capacitance-conductance-voltage characteristics under solar light. The photoconducting mechanism of the diodes were analyzed by the transient photocurrent measurements. It was found that the photoconductivity mechanism is controlled by the continuous distribution of trap levels. The diodes exhibited the photocapacitance and are changed with increasing Cu2O content. The presence of the interface states in the interface of the diodes was confirmed by the series resistancevoltage behavior. The obtained results indicate that the p-Si/Zn1-xAlxO-Cu2O/Al diodes can be used as a photosensor in optoelectronic applications

Thermal performance of heat pipes using nanofluids

The performance of conventional thermal systems which use heat transfer fluid (HTF) may be improved by adding nanoparticles within the HTF (nanofluid). However, the heat transfer capabilities of a nanofluid-charged heat pipe are relatively unquantified, and have remained somewhat controversial. This work reviews past studies focusing on the application of nanofluids in various types of heat pipes. Furthermore, full numerical simulation is then presented to account for the effect of nanofluids in a conventional heat pipe. Validation of the numerical model is performed through comparison to experimental tests for various nanoparticles. A revised Merit number is introduced for the performance evaluation of nanofluid-charged heat pipes. A parametric study is also included for the addition of Al2O3, CuO and TiO2 nanoparticles, and provides guidance towards better understanding of nanofluids and their effect on the thermal performance of heat pipes. The optimal nanoparticle concentration of Al2O3, TiO2 and CuO corresponding to the capillary limit for a conventional nanofluid-filled heat pipe was determined to be 25% by vol. for both Al2O3 and TiO2, and 35% for CuO. Overall, a maximum decrease in total thermal resistance was observed to be 83%, 79% and 76% for Al2O3, CuO and TiO2, respectively.

Study of ozone reactor with dielectric barrier discharge plasma (BDBP): variations of inner electrode based on Stainless steel, Galvalume, and Copper

The research of ozone reactor with dielectric barrier discharge plasma (BDBP) with variations of inner electrode based on stainless steel, galvalume, and copper has been done. The ozone was produced with oxygen as inputted gas. The ozone concentration has determined with variations of voltage (from 3 to 5 kV) and flow rate (i.e. 2,3,4,5,6,8 and 10 L/min). Ozone reactor, has a frame with cylinder-cylinder configuration. Inner electrode (cylindrical) made of stainless steel, galvalume and copper. The three of materials was used for evaluates the inner electrode's corrosion resistance characteristics for DBDP reactor. The outer electrodes (cylindrical) made of zinc plate, while Pyrex used as dielectric material. AC High Voltage was used as power supply with frequency of 16 kHz. This research has been conducted with five variations of reactor's length of 5, 10, 15, 20, and 25 cm. The ozone concentration has measured with KI solution and then titrated using sodium thiosulphate. After used as the inner materials of ozone reactor, the corrosion test has been conducted with SEM and EDX analysis. The results showed that ozone concentration was increasing by the increasing of voltage, and the greater gas flow rate gives the less ozone concentration. In addition, the most corrosion electrodes is one made of copper, which supported by SEM EDX result, that has CuO concentration of 60,77%. Otherwise, from the three of materials, stainless steel is obtained as the most stainless material.

Highly Efficient and Recyclable g-C3N4/CuO Hybrid Nanocomposite Towards Enhanced Visible-Light Photocatalytic Performance

A highly efficient visible-light-driven g-C3N4/CuO hybrid nanocomposite catalyst with different molar contents of CuO are successfully fabricated via a simple liquid phase synthesis process and applied to the degradation of Rhodamine B (RhB) solution. The results reveal that monodisperse CuO nanoparticles with a size of less than 10[Formula: see text]nm are uniformly distributed on the surface of g-C3N4nanosheets. Compared with the pure g-C3N4and CuO, the as-prepared nanocomposite displays significantly enhanced photocatalytic performance under visible-light irradiation. Attractively, the photocatalytic activities of the nanocomposite catalysts can be tuned by adjusting the molar ratio of g-C3N4and CuO. When the molar ratio reaches 2:1, the nanocomposite exhibits the highest photocatalytic activity, which can decompose RhB completely in 5[Formula: see text]min. The improved performance could be ascribed to the formation of heterostructure between g-C3N4and CuO as well as the decreased particle size of CuO, the presence of H2O2, large surface-exposure area and the suitable band position of g-C3N4/CuO nanocomposite. Interestingly, the nanocomposite shows excellent stability and recyclable property toward the photodegradation of RhB. Finally, a possible photocatalytic mechanism is proposed.

Characteristics of La0.6Sr0.4Co0.2Fe0.8O3–Cu2O mixture as a contact material in SOFC stacks

La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), a cathode material for solid oxide fuel cells, is mixed with six weight percentages (2.46–21.74 wt%) of more conductive Cu2O powder for use as a cathode contact material. Electrical conductivity change is measured at 800 °C for 600 h. Conductivity first increases with the Cu2O weight percentage to reach a peak value 30.67 S/cm at 7.18 wt%, then decreases with further more Cu2O content. Microstructural examination reveals that Cu2O oxidizes as CuO in the high temperature environment with a loose matrix, which can raise the electrical resistance. LSCF–Cu2O paste with three weight percentages of Cu2O is also applied in steel/paste/steel assemblies. The area specific resistance is measured at 800 °C for 200–300 h. It is found that LSCF-7.18 wt% Cu2O exhibits the lowest resistance. Additionally, stack performance is compared between two single-cell stacks with Ag mesh and LSCF-4.9 wt% CuO as the contact layer respectively. It shows that the LSCF-4.9 wt% CuO stack yields comparable power output with a lower degradation rate. Experimental results indicate that LSCF with 7.18 wt% Cu2O addition can serve as a potential contact material.

Thermal energy storage enhancement of a binary molten salt via in-situ produced nanoparticles

Thermal energy storage (TES) system is an essential component of any concentrating solar thermal power (CSP) plant to ensure a reliable plant operation even at night or cloudy weather. To enhance the TES capacity, a one-step method was proposed to synthesize nano-salts by in-situ production of CuO nanoparticles, via a high temperature decomposition of copper oxalate, in a binary salt used as a phase change material (PCM). The specific heat of the nano-salt both for solid and liquid phases were measured by differential scanning calorimetry (DSC) with the weight fraction of CuO nanoparticles varied from 0.1 to 3.0wt%. The maximum specific heat increment of 7.96% in solid phase and 11.48% in liquid phase, were achieved at a CuO nanoparticle concentration of 0.5wt%. A forming of intermediate layers composing of needle-like structures between nanoparticles and the salt was observed. The mixing model considering such an intermediate layer can be used to explain the observed specific heat enhancement at low particle concentrations. Both latent heat and onset temperature were decreased with increasing concentrations of CuO nanoparticles, while the melting temperature range was increased. When considering both latent heat and sensible heat contributions, the maximum increment of TES was achieved as 4.71% at 0.5wt% CuO concentration in the temperature range from 160°C to 300°C.

Structural characterization and calorimetric dissolution behavior of Na2O[sbnd]CuO[sbnd]P2O5 glasses

Two series of glasses belonging to the ternary system Na2O - CuO - P2O5 where copper is introduced differently were synthesized by the conventional melt-quenching technique. Both series start from meta-phosphate composition NaPO3 (50Na2O-50P2O5). In the first series, the Na2O/P2O5 ratio is constant (Na2O/P2O5=1) and both Na2O and P2O5 oxides were replaced by copper oxide CuO: (50-x/2) Na2O - xCuO - (50-x/2) P2O5, 0≤x≤40. In the second series, the molar percentage of P2O5 is kept constant at 50mol% and Na2O is replaced by CuO: (50-x)Na2O – xCuO – 50P2O5, 0≤x≤50. The glasses of these two series belong respectively to NaPO3-CuO and NaPO3-Cu(PO3)2 lines of the ternary system. These materials were characterized by density measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), Raman, diffuse reflectance and dissolution heat measurements carried out with micro-calorimetry technique. Introduction of copper in meta-phosphate glass induces a blue/green color, and strengthens the vitreous network, as shown by the decrease of the molar volume (VM) and the increase of the glass transition temperature (Tg) when the content of CuO rises. The crystallization of the glasses, followed by XRD, leads to the formation of NaPO3, Na2CuP2O7 or Na2Cu(PO3)4 depending on the composition. Raman spectroscopy shows the conservation of the metaphosphate chains for NaPO3-Cu(PO3)2 glasses characterized by a constant O/P ratio (O/P=3) and the depolymerization of these chains for NaPO3-CuO glasses where O/P ratio varies from 0 to 3.67. UV - visible study showed that the optical energy gap decreases by increasing the CuO concentration. Calorimetric study of the dissolution of glasses in acid solution shows a decrease of the dissolution enthalpy, for both series, when the CuO content increases. The dissolution phenomenon is endothermic for glasses with low content in CuO (x<30) and exothermic for glasses rich in CuO.

Synthesis and characterization of pure and (Ce, Zr, Ag) doped mesoporous CuO-Fe2O3 as highly efficient and stable nanocatalysts for CO oxidation at low temperature

A series of single and mixed oxide nanocatalysts of mesoporous CuO-Fe2O3 with different CuO contents (1–50wt.%) were prepared by a co-precipitation method and further promoted by trace amounts of CeO2, ZrO2 and Ag2O (0.1–0.5wt.%) dopants. The original and calcined catalysts were characterized by TG, DTA, XRD, TEM, VSM, N2 sorption analysis, surface chemisorbed oxygen and DC electrical conductivity measurements. The catalytic performance of these nanocatalysts toward CO oxidation was studied using a conventional fixed bed flow type reactor. The results revealed that the addition of 1–20wt.% CuO to Fe2O3 monotonically increases the specific surface area, the amount of surface chemisorbed oxygen, electrical conductivity and catalytic activity of the nanocatalysts. In addition, the catalytic activity indicated that Fe-Cu mixed oxide nanocatalyst promoted with the three dopants (CeO2, ZrO2 and Ag2O) exhibited the highest catalytic activity with a total conversion of CO into CO2 at 100°C. Moreover, the activation energy of CO oxidation decreased from 38.4 to 23.1kJmol−1 upon treating the catalyst containing 20wt.% CuO with the three dopants. Finally the effects of various operational parameters were also studied.

Geochemistry of river suspended sediments in tropical watersheds: anthropogenic and granite-gneiss sources, SE Brazil

ABSTRACTMineralogy and geochemistry of the total suspended sediment (TSS) from a granite-gneiss watershed in southeast Brazil brought light to geogenic and anthropogenic sources. TSS was sampled in 15 points along the Piabanha watershed in summer (February 2013) and winter (August 2013). The Piabanha watershed (2 × 103 km2) is located in the mountainous region of Rio de Janeiro, and it is an affluent of the Paraiba do Sul River, the most important river from the Brazilian southeastern coast. TSS mineralogical analyses were performed with X-ray powder diffraction. Geochemical analysis was done with energy dispersive X-ray fluorescence. Quartz, kaolinite and gibbsite were dominant in the TSS mineralogy, followed by feldspar and mica. Granite and gneiss rocks contribution in the TSS have a common mineralogical and geochemical source. But the alluvial deposits from river banks might have been responsible for the differences between summer and winter samples. The major features in TSS from geogenic sources were SiO2, Al2O3, MgO, Ga2O3, Nb2O5, Rb2O, K2O, SrO, ZrO2 and TiO2. The good correlation on the Si:Al molar ratio suggested that the source area is intensely weathered. Pollution features (sewage source) were given by significant TSS concentration of Fe2O3, MnO, ZnO, CuO, As2O3, CaO, Na2O, P2O5 and SO3.

Properties of ZnO-Cu_2-xSe thin films deposited by sputtering from composite ZnSe-Cu_2O targets

Amorphous and polycrystalline ZnO-Cu2-xSe composite thin films were deposited by rf sputtering using a single target prepared from mixtures of ZnSe and Cu2O powders. Films were grown from three different targets with Cu2O atomic concentrations of 12, 36 and 60% for substrate temperatures between room temperature and 400 °C. The transmittance, reflectance and electrical properties were dependent upon the Cu2O concentration in the target and on the substrate temperature. The optical properties of the polycrystalline films were determined by the copper selenide phases present in the films, which allows foreseeing applications as coatings for windowpanes with strong infrared rejection. The electrical characterization showed that the ZnO-Cu2-xSe composite films are n-type with resistivity values in the range from 3x10−3 to 3x103 Ω⋅cm.

The study on preparation and the effect of adsorption over photocatalytic activities of Cu2O/titanate nanotubes (Cu2O/TNTs)

Cu2O-loaded titanate nanotubes (Cu2O/TNTs) were prepared by ultrasonication-assisted Cu2+ impregnation reduction method. Experiment shows that the Cu2O nanoparticles (with diameter of 3nm) were uniformly distributed on the TiO2 nanorods (with diameter of 20nm). The deposition of Cu2O breaks the nanotubes into nanorods and blocks the neck. The N2 adsorption–desorption experiments indicates that the Cu2O/TNTs surface area decreased with the increase of Cu2O content. The Cu2O/TNTs nanocomposites presents two absorption edges in UV–vis DRS, and the absorption intensity at visible light region increased with the increase of Cu2O in the Cu2O/TNTs while the UV region keeps constant. The adsorption kinetics and visible light irradiated photodegradation kinetics of Cu2O/TNTs on methylene blue was systematically investigated. Experiment demonstrates that the adsorption of MB to the catalysts surface is vital for the heterogeneous photocatalysis.

Spectroscopic features of copper ions in multi-component Na2O[sbnd]PbO[sbnd]Bi2O3[sbnd]SiO2 glass ceramics

Multi-component Na2OPbOBi2O3SiO2 glasses were crystallised with different CuO contents (0–1 mol % in steps of 0.2) as nucleating agent. These glass ceramics were characterized by XRD, SEM and DTA techniques and indicated the samples contain well defined and randomly distributed grains of different crystalline phases. Spectroscopic studies viz., optical absorption, EPR, FTIR and Raman were also carried out on these glass ceramics. The broad absorption band observed in the wavelength region 550–1000 nm in these glass ceramics and is the characteristic of Cu2+ ions. Optical absorption and EPR studies suggest that Cu2+ ions enter into the lattice as tetragonally distorted octahedral symmetry for which the bonding parameters were evaluated. FTIR and Raman spectra give important information about the nature of various structural units in the glass ceramic matrix. The analysis of these spectroscopic investigations reveals that with increase in the concentration of nucleating agent CuO, copper ions exist in Cu2+ state they act as modifiers and increases the degree of disorder in the glass ceramic network.

Ionic Liquid Assisted Hydrothermal Syntheses of TiO2/CuO Nano‐Composites for Enhanced Photocatalytic Hydrogen Production from Water

AbstractHetero‐junction TiO2/CuO nano‐composite (NC) photocatalysts for hydrogen production from water were synthesized. A comparison of the photocatalytic activity obtained from the photocatalysts synthesized by conventional hydrothermal method (HM) and by ionic liquid assisted hydrothermal method (ILAHM) is provided. The composite nature and other physico‐chemical properties were investigated via thorough characterizations. Effect of thermal treatment conditions such as temperature and time on crystalline structure, surface area, quantum yield, band gap and hydrogen production activity of TiO2/CuO NCs has been studied comprehensively. The concentration of CuO in TiO2 matrix has been fine‐tuned to improve the hydrogen production. The synergy between the CuO and TiO2 has an optimum for concentration of 25 wt % of CuO in NCs synthesized by ILAHM, whereas it is 50 wt% of CuO in NCs synthesized by HM. Compared to the NCs prepared by conventional HM; the samples prepared by ILAHM have presented enhanced photocatalytic hydrogen production showing ILAHM as a potential synthesis route. The optimized NC prepared by ILAHM has produced promising hydrogen evolution of 8670 µ mol/g under the illumination from Xenon/Mercury lamp in water/ethanol system. The enhanced hydrogen evolution attributed to its porous like surface morphology, higher surface area and quantum yield.

CuO Quantum Dots Embedded in Carbon Nanofibers as Binder‐Free Anode for Sodium Ion Batteries with Enhanced Properties

The design of sodium ion batteries is proposed based on the use of flexible membrane composed of ultrasmall transition metal oxides. In this paper, the preparation of CuO quantum dots (≈2 nm) delicately embedded in carbon nanofibers (denoted as 2-CuO@C) with a thin film via a feasible electrospinning method is reported. The CuO content can be controlled by altering the synthetic conditions and is optimized to 54 wt%. As binder-free anode for sodium ion batteries, 2-CuO@C delivers an initial reversible capacity of 528 mA h g-1 at the current density of 100 mA g-1 , an exceptional rate capability of 250 mA h g-1 at 5000 mA g-1 , and an ultra-stable capacity of 401 mA h g-1 after 500 cycles at 500 mA g-1 . The enhancement of electrochemical performance is attributed to the unique structure of 2-CuO@C, which offers a variety of advantages: highly conductive carbon matrix suppressing agglomeration of CuO grains, interconnected nanofibers ensuring short transport length for electrons, well-dispersed CuO quantum dots leading to highly utilization rate, and good mechanical properties resulting in strong electrode integrity.

Supported Photocatalyst Based on CuO–TiO2/Palygorskite Nanocomposite Material for Wastewater Treatment

This study deals with the immobilization of mixtures of two semiconductor oxides CuO and TiO2 on fibrous palygorskite clay mineral in order to evaluate their photocatalytic activity for removing Orange G dye as model pollutant from aqueous solutions. The elaboration of CuO–TiO2/Palygorskite nanocomposites was carried out by impregnation with Cu2+ of before hand synthesized TiO2 supported palygorskite (Pal) followed by air annealing for 5 h at 550 °C. In the composite materials, different CuO to CuO + TiO2 molar ratios were used in order to obtain a CuO content in the range 13–30 mol.%. XRD, SEM and TEM equipped with elemental EDS analysis are concordant for showing the crystallization of anatase TiO2 along with CuO whose average size of nanoparticles (NPs) are in the range 6 to 20 nm as determined by TEM. By increasing the CuO content the average size of this oxide remains constant at about 10 nm while that of TiO2 NPs is slightly decreasing from 8.4 to 5.1 nm. Both oxide NPs were successfully attached on palygorskite fibers where they form CuO–TiO2 heterojunctions (grain boundaries like). The CuO–TiO2/Pal supported photocatalyst containing 23% of CuO was found to be the most photoactive material but itremained less active than TiO2/Palygorskite supported photocatalyst. The photocatalytic activity of the mixed nanocomposites is not readily correlated with only one of their main features as CuO content or the average crystallite size of functional oxides indicating that if there are synergistic effects there are also antagonistic effects in particular for high CuO contents.

The modification of BaCe0.5Zr0.3Y0.2O3–δ with copper oxide: Effect on the structural and transport properties

The effect of the content of CuO additive on the sinterability, phase composition, microstructure, and electrical properties of BaCe0.5Zr0.3Y0.2O3–δ proton-conducting material is studied. Ceramic samples were produced by the citrate–nitrate synthesis method with the addition of 0, 0.25, 0.5, and 1% CuO. It is shown that the relative density of the samples containing 0.5 and 1% CuO is higher than 94% at a sintering temperature of 1450°C, whereas the relative density of the material is no higher than 85% at a lower content of the sintering additive. From the data of X-ray diffraction analysis and scanning electron microscopy, it is established that the introduction of a small CuO content (0.25%) is inadequate for single-phase and high-dense ceramics to be formed. The conductivity and scanning electron microscopy data show that the sample with BaCe0.5Zr0.3Y0.2O3–δ + 0.5% CuO composition possesses high total and ionic conductivities as well as a high degree of microstructural stability after hydrogen reduction of the ceramics. The citrate–nitrate method modified by the introduction of a small CuO content can be recommended for the production of single-phase, gas-tight, and high-conductivity electrolytes based on both BaCeO3 and BaZrO3.

High-efficient n-type TiO2/p-type Cu2O nanodiode photocatalyst to detoxify hexavalent chromium under visible light irradiation

n-Type TiO2/p-type Cu2O nanodiode photocatalyst with different Cu2O contents had been successfully synthesized. The nanocomposite also had been well characterized and tested for its photocatalytic activity toward reduction of 10 ppm K2Cr2O7 aqueous solution under visible light illumination. It was found that 30 % Cu2O loading in the nanocomposite had the best photocatalytic activity in detoxifying Cr(VI) without any hole scavenger agents and the solution pH adjustment. As a result, water was simultaneously oxidized by photogenerated holes to evolve oxygen. The 20 mg as-prepared TiO2/Cu2O nanocomposites could reduce almost 100 % of 10 ppm K2Cr2O7 aqueous solution in 90 min under 150 W halogen lamp illumination. From the results, it was concluded that the photocatalytic activities of p–n heterojunction of TiO2/Cu2O nanodiodes had proven to be an efficient photocatalyst under visible light illumination. The photocatalytic performances of TiO2/Cu2O nanocomposites and its photoreaction mechanism were proposed and discussed in this work.