Cu In Air Research Articles

Preparation of flame retardant and antibacterial polyacrylonitrile based on Cu2+ chelated six-armed star-type flame retardant SCCP and chitosan

In this work, a six-armed star-type flame retardant (SCCP) contained phosphorus, nitrogen and sulfur contents was developed, which was then combined with chitosan (CS) to chelate Cu2+ (SCCP@CS-Cu) and blend with polyacrylonitrile (PAN) to produce flame retardant and antibacterial PAN composite (PAN/SCCP@CS-Cu). TG showed that the residual char of PAN/SCCP@CS-Cu in air and nitrogen atmosphere was as high as 16.41 % and 48.48 % at 800 °C, respectively, which were greater than that of PAN. The LOI value of PAN/SCCP@CS-Cu improved to 33.0 % and the peak heat release rate (PHRR) and total heat release (THR) of the composite were all greatly reduced. In addition, the total smoke production (TSP) of PAN/SCCP@CS-Cu decreased by 73.6 % compared to the control sample. Interestingly, the antibacterial properties of PAN/SCCP@CS-Cu against E. coli and S. aureus reached 98.45 % and 99.33 %. This work provides an insight into developing an environmentally friendly PAN composite with flame retardancy, smoke suppression and antibacterial properties, greatly expanding its application field.

Screening Surface Structure–Electrochemical Activity Relationships of Copper Electrodes under CO2 Electroreduction Conditions

Understanding how crystallographic orientation influences the electrocatalytic performance of metal catalysts can potentially advance the design of catalysts with improved efficiency. Although single crystal electrodes are typically used for such studies, the one-at-a-time preparation procedure limits the range of secondary crystallographic orientations that can be profiled. This work employs scanning electrochemical cell microscopy (SECCM) together with co-located electron backscatter diffraction (EBSD) as a screening technique to investigate how surface crystallographic orientations on polycrystalline copper (Cu) correlate to activity under CO2 electroreduction conditions. SECCM measures spatially resolved voltammetry on polycrystalline copper covering low overpotentials of CO2 conversion to intermediates, thereby screening the different activity from low-index facets where H2 evolution is dominant to high-index facets where more reaction intermediates are expected. This approach allows the acquisition of 2500 voltammograms on approximately 60 different Cu surface facets identified with EBSD. The results show that the order of activity is (111) < (100) < (110) among the Cu primary orientations. The collection of data over a wide range of secondary orientations leads to the construction of an “electrochemical–crystallographic stereographic triangle” that provides a broad comprehension of the trends among Cu secondary surface facets rarely studied in the literature, [particularly (941) and (741)], and clearly shows that the electroreduction activity scales with the step and kink density of these surfaces. This work also reveals that the electrochemical stripping of the passive layer that is naturally formed on Cu in air is strongly grain-dependent, and the relative ease of stripping on low-index facets follows the order of (100) > (111) > (110). This allows a procedure to be implemented, whereby the oxide is removed (to an electrochemically undetectable level) prior to the kinetic analyses of electroreduction activity. SECCM screening allows for the most active surfaces to be ranked and prompts in-depth follow-up studies.

Multi-Scale Application of Advanced ANN-MLP Model for Increasing the Large-Scale Improvement of Digital Data Visualisation Due to Anomalous Lithogenic and Anthropogenic Elements Distribution

The main objective of this paper is to compare and improve spatial distributions models for Pb and Cu in air and soil using the universal kriging and ANN-MLP at the macro regional scale. For this purpose, both models have been applied for visualization of a spatial distribution of lead (Pb) and copper (Cu) in a morphologically and geologically complex area. Two river basins in the eastern part of North Macedonia, have been selected as the main research region due to the extensive anthropogenic impact of long-lasting mining activities, with emphasis on the specific geochemistry of the area. Two environmental media (soil and moss) have been selected as they are much more available as space from biospheres submitted for destruction processes globally. Surface soil and moss as bio-indicator element measurements were submitted in correlation with geospatial data obtained from DEM, land cover data, and remote sensing, and are incorporated into spatial distribution mapping using an advanced prediction modeling technique, ANN-MPL. Both methods have been further compared and evaluated. The comparative data outputs have led to the general conclusion that ANN-MPL gives more realistic, reliable, and comprehensive results than the universal kriging method for the reconstruction of main distribution pathways. The more the factors influencing the process of distribution of the elements increase, the more the use of ANN-MPL improves.

Ultrafast synthesis of Cu2O octahedrons inlaid in Ni foam for efficient alkaline water/seawater electrolysis

Development of bifunctional cost-effective and self-supporting electrocatalysts for high-performance water/seawater electrolysis are vital for emerging energy storage and conversion technologies. Herein, an ultrafast strategy is reported to synthesis homogeneous Cu2O octahedrons inlaid in Ni foam (oct_Cu2O-NF) via spontaneous replacement of Ni with Cu, followed by rapid oxidization of Cu in air. Benefiting from the high dispersion of uniform octahedral structure and strong interaction between Cu2O and Ni foam, oct_Cu2O-NF displayed a superior activity for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) as well as outstanding stability. After assembling oct_Cu2O-NF as bifunctional electrodes for alkaline seawater splitting, the electrolyzer exhibited a very small cell voltage of 1.71 V to reach 10 mA cm−2. This brand-new way of ultrafast synthesis for oct_Cu2O-NF experimentally confirms the feasibility of Cu-based nanomaterials for efficient water/seawater electrolysis.

Nanosecond and sub-nanosecond laser-assisted microscribing of Cu thin films in a salt solution

Pulsed laser-based material removal is a preferred technique for microscribing of copper (Cu) film coated on polymers, as the pulse width limits the heat diffusion. However, experimental studies have shown that microscribing of Cu in air results in recast/redeposit formation and oxidation. Although the water medium can reduce these effects to a certain extent, the material removal rate is lesser for Cu. This article reports the influence of laser pulse duration on a hybrid method to enhance the pulsed laser-assisted microscribing of a copper thin film in the presence of an environmentally friendly sodium chloride salt solution (NaCl). The focused laser beam irradiation of Cu film results in ablation with a temperature of the zone well above the boiling point of Cu, which in turn, can assist in accelerating the chemical reaction. In this hybrid scribing technique, along with laser-based material removal, laser-activated chemical etching also helps in removing the material selectively. A sub-nanosecond laser with a pulse width of 500 ps (picosecond [ps] laser) and a nanosecond laser with a pulse width of 6 ns (nanosecond [ns] laser), with a wavelength of 532 nm, are used to understand the influence of laser pulse duration on this hybrid material removal mechanism. Hybrid microscribing with the ps- and ns lasers in salt solution resulted in an increase in the channel depth by ≈5 µm and ≈9 µm, respectively, compared to the channel depth obtained in deionized water. The theoretical model shows that during the ns laser ablation, the cooling rate is slower, resulting in a high temperature in the ablation zone for a longer duration and improved material removal.

Rapid pressureless and low-temperature bonding of large-area power chips by sintering two-step activated Ag paste

Pressureless and low-temperature sintering of Ag paste has been mentioned as a promising strategy to solve the poor performance of large-area chips. In this paper, we develop a two-step surface activation process to achieve rapid pressureless and low-temperature bonding of Cu in air using a micron-scale Ag paste for large-area chips. The organics that adsorb on the Ag particles are initially removed by oxygen plasma cleaning, and the silver oxide byproducts are subsequently deoxidized by a methanol/hydroxide mixed vapor treatment. The two-step activation significantly improves the sinterability of the micron-scale Ag paste, leading to excellent interfacial properties after rapid sintering at 200 °C for only 10 min in air. Robust-bonded joints are achieved with a shear strength and thermal conductivity that are four times higher than those of the non-activated bonded joints. The bonding strength and thermal conductivity of the Cu joint structure are approximately 25 MPa and 96 W/mK, respectively, which are superior to those of traditional Sn–Pb solders. Void-free bonding interfaces are confirmed by large-area chips even without pressure in air; this method shows great potential for the cost-effective commercial packaging of power electronics.

The impact of defect density, grain size, and Cu orientation on thermal oxidation of graphene-coated Cu

Graphene has been shown to be a promising barrier for thermal corrosion due to its low gas and liquid permeability; however, there have been contradictory reports in the literature regarding the mechanisms of oxidation of graphene-coated Cu. This work systematically investigates the effect of chemical vapor deposited graphene grain size, point defect density, and underlying Cu orientation on the thermal oxidation of the underlying Cu in air. For graphene with either small grain size (~0.04–0.4 μm2) or large point defect density (~800 μm−2), oxidizers have relatively unhindered access through these defects to corrode the underlying Cu, and the corrosion is relatively independent of Cu orientation. For graphene with low defect density, the rate of Cu oxidation depends on the Cu crystal orientation on which the graphene is synthesized. Graphene-coated Cu (110) is completely corroded in just 2 min of thermal oxidation at 250 °C, while no surface oxidation for graphene-coated Cu (111) is observed for the same conditions. Thus, corrosion of graphene that is synthesized to achieve large grain size (>~170 μm2) is limited by the weakest graphene/Cu orientation interaction, not the size of the graphene grains, as was previously assumed.

Induction brazing BaCo0.7Fe0.2Nb0.1O3-δ membrane tubes to steel supports with Ag-based filler in air

An induction brazing process has been developed to seal BaCo0.7Fe0.2Nb0.1O3-δ (BCFN) membrane tubes to metal supports using Ag-Cu alloy in air. The closed-one-end BCFN membrane tubes with an outer diameter of 16mm and a length of 560mm were prepared by slip casting. The thermal expansion behaviors of the BCFNO membrane, Ag braze and 310S stainless steel were characterized. A sleeve joint was optimized to reduce the stresses caused by the mismatching in thermal expansions. Ag-1mol%Cu braze was chosen as brazing filler duo to its good wettability for both the membranes and the metal substrates and thin and continuous reaction layers. Based on the characteristics of the BCFN membrane, a temperature schedule was exploited to successfully achieve the induction brazing of the BCFN membrane tubes to the 310S supports using Ag-1mol%Cu in air. The entire time needed is about 80min. The brazed assemble subjected to 15 thermal cycles still exhibits no degradation in joint hermeticity and stable oxygen permeation flux. The result indicates that induction brazing can efficiently join large membrane tubes with high thermal expansion to their metal supports.

A facile fabrication of Cu2O nanowire arrays on Cu substrates

Abstract Nanomaterials play an important role in modern science and engineering. The ability to fabricate nanomaterials with high quality and low cost is a primary stage for further discovering their applications. This research article presents a facile fabrication of Cu2O nanowires on Cu substrate. It was found that simply heating Cu in air leads to the growth of Cu2O nanowires. The Cu2O nanowires are aligned in one direction and vertically grown on the Cu substrate. The growth process of nanowires was tracked by SEM and the root at the initial stage was observed by HRTEM. The access to oxygen is critical to the growth of Cu2O nanowires and the patterned nanowire arrays can be readily fabricated by using a mask. The method reported here offers a great potential route toward a large scale manufacture of Cu2O nanowires.

Synthesis and friction properties of copper/PMMA composites by soapless emulsion polymerization

AbstractCopper (Cu)‐doped polymethylmethacrylate (PMMA) composites were prepared by soapless emulsion polymerization. In this process, copper nanoparticles were modified by sodium oleate (SOA) and the surface property of Cu nanoparticles changed from hydrophilic to hydrophobic. The hydrophobic Cu nanoparticles could not only avoid the oxidation of Cu in air but also improve the compatibility between Cu nanoparticles and PMMA. The TEM micrographs revealed that Cu nanoparticles were encapsulated in PMMA polymer microspheres. In addition, the uniform Cu/PMMA composite microspheres could be synthesized in such a soapless emulsion polymerization process. It was worth mentioning that the friction property in oil was well improved when little nanocomposites were added into the base oil, which indicated that the composites can be widely used in lubricating oil. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Transmission of Voltage Pulses through the Cu Single-Atom Contact

We have conducted a pulse transmission experiment on the single-atom contact of Cu in air at room temperature. Employing a thin coaxial cable as a sample of the mechanically controllable break junction (MCBJ) method, we can produce stable Cu single-atom contacts and transmit through them pulses of 50–500 ns width. Analysis of the detected signal waveform indicates that a Cu single-atom contact behaves as a pure resistance, which is consistent with the theoretical admittance of quantum point contacts.

Correlation between outward diffusion of additives and oxidation of Cu(3.9at.%Ti) and Cu(2.3at.%Ta) thin films

Thin films of pure Cu and Cu alloys (with 3.9at.% Ti or 2.3at.% Ta) are deposited on SiO2∕Si substrates by magnetron sputtering. Upon annealing at 700°C in vacuum for 30min, Ti in the Cu(3.9at.%Ti) films will mostly diffuse to the free surface, but the majority of Ta in the Cu(2.3at.%Ta) film remains within the Cu layer. The outward diffusion of Ti or Ta strongly influences the oxidation of Cu in air. The degree of Cu oxidation was determined by glancing incident angle x-ray diffraction and the normalized sheet resistance. Oxidation test shows that the Cu(3.9at.%Ti) films exhibit a superior oxidation resistance when oxidized at 200°C in air, especially for the Cu(3.9at.%Ti) film which has been preannealed at 700°C in vacuum. But the Cu(2.3at.%Ta) film with the same preannealing treatment only slightly improves the oxidation resistance, in comparison with the pure Cu film. The correlation between outward diffusion of additives and oxidation of Cu in the Cu(3.9at.%Ti) and Cu(2.3at.%Ta) thin films is discussed.

Active Soldering of Indium Tin Oxide (ITO) With Cu in Air Using an Sn3.5Ag4Ti(Ce, Ga) Filler

Indium tin oxide (ITO) ceramics are bonded with ITO and Cu at 250 °C in air using an active solder Sn3.5Ag4Ti(Ce, Ga). The mechanism for such low temperature soldering of ITO ceramics in air has been investigated. Electron probe microanalyzer (EPMA) analyses reveal that the element oxygen distributes uniformly within the solder matrix after soldering, while Ti segregates effectively at the ITO/solder and Cu/solder interfaces at such a low temperature, giving satisfactory joining results of Cu/Cu, ITO/ITO, and ITO/Cu in air.

Microstructural characterization of internal oxidation of AgCu alloy

The internal oxidation of AgCu alloys with atomic percentage 0.8, 3.3, 6.3 and 9.5 of Cu in air at 750 degrees C and 850 degrees C has been studied. It was found that CuO particles precipitated homogeneously on the surface ai AgCu alloys except for Ag-9.5% (atomic percentage) Cu. The latter exhibited the agglomerated precipitation of CuO particle cluster on the surface. The experimental results also revealed that the nucleation and growth of CuO oxide evidently varied with the change of Cu contents or oxidation temperature. When both Cu content and exposure temperature were low, the precipitation and the growth of internal CuO oxide were consistent with the prediction by the classical Bohm-Kahlweit mode, but the abnormal phenomenon of nucleation and growth of the CuO oxide was observed when the Cu content or the exposure temperature was increased. As a result of investigation of the atomic structure of different internally oxidized AgCu alloys, it is proposed that the stacking fault tetrahedra(SFT), which were found in the oxidized alloys, promoted the nucleation of CuO internal oxide.

Laser ablation of Si, Ge, ZrO2 and Cu in air

Si, Ge, ZrO2 and Cu were irradiated by air by 1.06 mu m 10 ns laser pulses with a high intensity of 6.4*109 W cm-2. Detailed scanning electron microscopy (SEM) and ablation crater profile measurements were made. The results indicated that the ablation rates of these materials under intense pulsed laser irradiation are quite high. The refractory oxide ZrO2 has the highest material removal rate. Evidence of liquid material flushed out of the ablation craters was observed for all the materials studied with the exception of Cu. Gas dynamic velocities of transient thermal vaporization were calculated using self-similar solutions of the gas dynamic equations. Using these parameters, material removal rates were calculated and the results compared with the experimentally measured values. Possible ablation mechanisms of these materials under the irradiation conditions used in the present work were discussed.