Temperature Of Cu Research Articles

Enhanced cross-interfacial growth by thickening transition layers and tailoring grain size of columnar nanotwinned Cu films

Electrodeposited <111>-oriented nanotwinned Cu (NT-Cu) films consist of micron-scale columnar grains and they are thermally stable up to 400 °C. By adding nanoscale equiaxed Cu grains at the bottom of the NT-Cu films, anisotropic large grain growth could be triggered below 200 °C. The grains grew over 50 μm in bonded Cu–Cu films with 5.7 μm thick. Two main factors are identified for the low thermal stability and large grain growth behavior. The grain refining and transition layer thickening are effective to lower the thermal stability of the NT-Cu and reduce the required temperature for recrystallization and grain growth in the NT-Cu film. By increasing the fine-grained layer and refining the grain size of the columnar twinned grains, anisotropic grain growth can occur at 150 °C. The low thermal stability NT-Cu can be employed to completely eliminate the bonding interface at low temperatures in Cu–Cu joints. However, when the fine-grained layer is thicker than a threshold value, normal grain takes place and the bonding interface remains. The mechanism of anisotropic large grain growth was also proposed.

Increased tensile strength induced by the precipitation of nanocrystals for welding joints of Zr-based amorphous alloys

Zr-based amorphous alloys have attracted intensive attention for applications because of their excellent mechanical property. However, the welding process is inevitable for some special cases, such as the obtain of large size structure parts. It is significant to clarify the influence of introduced welding joints on mechanical properties in Zr-based amorphous alloys. Herein, the increased tensile strength of welding joints in Zr-based amorphous alloys is demonstrated by choosing a suitable initial temperature of Cu cooling fixtures for pulsed laser welding. It is found that an optimized tensile strength is observed when the initial temperature is −20 °C. With the decrease of the initial temperature from 10 to −30 °C, the tensile strength shows a trend of first increasing and then decreasing. Combined with the characterization of microstructures, it can be concluded that the increased tensile strength results from the precipitation of nanocrystals in the heat affected zone. Thus, our results provide a method to improve the mechanical property by controlling the microstructures of the heat affected zone in welding joints of Zr-based amorphous alloys.

Stamped production of single-crystal hexagonal boron nitride monolayers on various insulating substrates

Controllable growth of two-dimensional (2D) single crystals on insulating substrates is the ultimate pursuit for realizing high-end applications in electronics and optoelectronics. However, for the most typical 2D insulator, hexagonal boron nitride (hBN), the production of a single-crystal monolayer on insulating substrates remains challenging. Here, we propose a methodology to realize the facile production of inch-sized single-crystal hBN monolayers on various insulating substrates by an atomic-scale stamp-like technique. The single-crystal Cu foils grown with hBN films can stick tightly (within 0.35 nm) to the insulating substrate at sub-melting temperature of Cu and extrude the hBN grown on the metallic surface onto the insulating substrate. Single-crystal hBN films can then be obtained by removing the Cu foil similar to the stamp process, regardless of the type or crystallinity of the insulating substrates. Our work will likely promote the manufacturing process of fully single-crystal 2D material-based devices and their applications.

Effect of non-Planckian spectrum on shock velocities and subsonic to transonic transition in mid-Z witness plate elements

In this work, we obtain the shock velocities in mid-Z elements, namely, Al, Ti, and Cu by performing radiation hydrodynamic simulations using constant radiation drives consisting of equilibrium Planckian distribution along with high-energy Gaussian profiles. The drive temperatures have been varied from 80 to 270 eV, and the fraction of total energy density due to Gaussian distribution (α) changes from 0 to 0.4. Though the shock velocity in all the three elements rise with the strength of the drive temperature, its variation with α is quite complicated. Using simulations, we have shown that rear surface expansion is not responsible for the observed variation in shock velocity with the fraction of hard x rays at various temperatures and explained it in terms of distribution of total extinction coefficient over the spectral form of incident drive source leading to change in albedos. The percentage variations in shock velocities are found to be commensurate with those in albedos as expected for x-ray driven ablation process. Accurate scaling laws relating the drive temperatures with the shock velocities and α have also been obtained. In Al, subsonic to transonic transition temperature is found to increase with α, whereas in Ti it is found to decrease. We have explained the variation in transition temperature in terms of Mach number. As this transition temperature in Cu is anticipated to be high due to its higher atomic number and density, we did not observe any transition up to the temperature (500 eV) considered in this paper.

Computational investigation of homogeneous-heterogeneous reactions in fluid with transport mechanisms: A finite element simulations approach

There are numerous applications in engineering and industry for homogeneous and heterogeneous chemical reactions in fluid regimes under the influence of nanoparticles and hybrid nanoparticles. This article models homogeneous and heterogeneous chemical reactions in the flow of polymer liquid (glycerin) containing Cu-Al2O3 in the presence of heat and mass transfer. The finite element method is used to quantitatively solve these models. A 76% increase in wall shear stress for the case of simultaneous dispersion of Cu and Al2O3 in comparison of only dispersion of Cu is noticed. Similarly, 44% increase in wall heat flux in noticed due to dispersion Cu and Al2O3 in comparison of dispersion of Cu only. The vortex parameter is responsible for a significant increase in the macro-motion of the fluid particles. Macro-motion gets more influence of micro motion than the influence of micro-motion on the macro-motion of Cu-Al2O3- polymer. To control momentum boundary layer thickness, reduce the diameter of the circular pipe. Magnetic force has the opposite direction of flow. Therefore, fluid motion is a decreasing function of magnetic field intensity. Further, the Lorentz force (magnetic force) for the case of Cu-Al2O3 - polymer is stronger than that for the case of Cu- polymer. Additionally, it can be seen that Cu-Al2O3- polymer experiences more Joule heating than Cu- polymer does. The micromotion is compromised when the curvature parameter is increased. As a result, convective transport slows down and the temperature of Cu- polymer and Cu-Al2O3 - polymers decreases. The result, the rate of conversion of electrical energy into heat speeds up intensity of magnetic field increase as and therefore, fluid temperature increases.

2-D Dynamic Excitation Temperature of Cu+ Under Diffuse Mode in Vacuum Arc

Cu I (Cu neutrals) excitation temperature is usually measured by researchers while analyzing vacuum arcs (ignited by CuCr electrodes). Since ions may have information that neutrals do not have, measuring Cu II (Cu <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{+})$</tex-math> </inline-formula> might reveal some new features of the vacuum arc. In this article, Cu II excitation temperature is measured by observing seven Cu II lines. Measurement results show the existence or not of a Cr component in a vacuum arc can greatly change the 2-D distribution pattern of Cu II excitation temperature (researchers suggest no influence on Cu I); from a “flat” shape changes to a “columnar” or a “bowl” shape (related to gap length). However, the Cr ratio in CuCr electrodes does not cause a noticeable difference both in Cu II excitation temperature value and in 2-D distribution shape. In the case of CuCr electrodes, before the arc mode change to anode spot mode, a new phenomenon occurs under diffuse mode; as the arc current grows higher than a critical value under a certain length of the gap, the temperature starts to drop in the area near the anode surface, forming a temperature valley. This temperature valley can be interpreted as a local increase in Cu II density. The local ion eruption caused by the Cr component might be a trigger or a pre-process for arc mode changing to anode spot mode.

Effect of Spark Plasma Sintering Temperature on Phase Evaluation and Mechanical Behaviour of cu- 4 Wt% SiC Composite

Spark plasma sintering (SPS) is a novel approach to fabricate Cu- SiC composites which have a relatively broad range of potential uses in space applications. The Cu- 4 wt% SiC composite with homogeneously dispersed SiC particles has been successfully synthesized at various SPS temperatures. In this study, the effect of SPS temperatures on the phase evaluation and mechanical characteristics of the Cu- 4 wt% SiC composite was investigated. From the results, it was confirmed that the optimum sintering temperature for Cu- 4 wt% SiC composite is 950°C. Raising the spark plasma sintering temperature from 850°C to 950°C led to a higher concentration of copper-liquid phase which accelerates the SiC particle rearrangement and fills the interstitial voids present in the interfaces of matrix and reinforcements which improves the mechanical properties of the Cu- 4 wt% SiC composite. However, increasing the SPS temperature by more than 950°C prone to the generation of the copper net and inhomogeneous SiC particle dispersion in the copper phases and declines the performance characteristics of the synthesized composite. The Cu- 4 wt% SiC composite sintered at 950°C exhibits superior mechanical characteristics than the composite sintered at 850°C, 900°C and 1000°C.

Influence of processing innovations on joint strength improvements in friction stir welded high strength copper alloys

One of the major challenges in welding the Cu–Cr–Zr alloys is that the high welding temperature often causes the coarsening of the precipitates, resulting in lower joint strength. Various strategies were studied to reduce the welding temperature below the aging temperature for limiting the precipitate coarsening. The results showed that great challenges existed in reducing the friction stir welding (FSW) temperature below the peak-aging temperature of Cu–Cr–Zr alloy (420–480 °C) without using coolant. Through softening the Cu–Cr–Zr alloys to the supersaturated solid solution state prior to FSW, the peak temperature during FSW of Cu–Cr–Zr alloy under water was reduced to ∼481 °C, which is close to the aging temperate of the Cu–Cr–Zr alloy. After post-weld aging heat treatment, the stir zone exhibited higher hardness than the peak-aged Cu–Cr–Zr alloy due to the combination of the high density of precipitates 10.5 nm in diameter and refined grains 0.65 μm in diameter, enabling the achievement of high joint strength equal to the peak-aged base metal. In addition, the FSW zone also exhibited a high electrical conductivity of 88.9% IACS, which is higher than that of the peak-aged base material (81.0% IACS).

Catalytic activity of Cu/H-ZSM-5 zeolite for the removal of oxygen in the landfill gas

The upgrading of landfill gas (LFG) to bio-methane is a feasible scheme to make full use of its energy and solve the environmental pollution problems caused by its emissions. In the process of LFG upgrading, deoxygen is an essential procedure. In order to develop highly efficient and low-cost catalysts for LFG deoxygen, a series of Cu/H-ZSM-5 zeolites with the content of copper (Cu) in the range of 0.95 wt%-10.48 wt% were prepared by incipient wetness impregnation method, and used in the removal of oxygen in simulated LFG. The results of deoxygen experiments showed that the Cu/H-ZSM-5 zeolite had an excellent catalytic activity comparable to noble-metal based catalysts. The light-off temperature of Cu(3.63)/H-ZSM-5 was as low as 321 °C under the experimental conditions with a gas hourly space velocity (GHSV) of feed gas (55 vol% methane, 1 vol% oxygen and 44 vol% carbon dioxide) at 68,790 h−1. According to the characterization results of the catalysts, it was supposed that the excellent catalytic deoxygen performance of the Cu/H-ZSM-5 zeolite might be mainly due to that it contains a variety of highly dispersed active Cu species, which could significantly reduce the activation energy barrier of methane. This work provides new insights into the development of low-cost high-performance LFG deoxygen catalysts in practical LFG upgrading engineering applications.

Elemental study of Devarda’s alloy using calibration free-laser induced breakdown spectroscopy (CF‒LIBS)

In the present study, we present the compositional analysis of a Devarda’s alloy using the calibration–free laser-induced breakdown spectroscopy (CF-LIBS) technique. A nanosecond pulsed Q-switched Nd:YAG laser was focused on the target-sample under investigation to ablate its surface and the measured emission spectrum was registered by using a spectrometer (LIBS2000+) having the optical spectral within a range from 200–720 nm. The analysis of the measured optical spectra confirms the presence of three major elements Aluminum (Al), Copper (Cu), and Zinc (Zn) in the target sample. The emission intensity line profiles of Zn, Cu, and Al were utilized to estimate the plasma-parameters consisting of excitation temperature, and the plasma number density. The plasma excitation temperature was investigated using the Boltzmann-plot technique, which yields the temperature for Cu and Zn as 8547 ± 5% K and 8100 ± 5%, respectively, while the electron plasma density was calculated from the Stark-broadening of individual neutral emission lines of Al, Cu, and Zn. For the quantitative analysis of the elements that exist in the target sample, a CF-LIBS technique was employed by assuming the condition of optically thin plasma as well as local thermodynamics equilibrium. Using the CF-LIBS technique, the relative composition in the form of weight percentage was estimated to be Zn: 57%, Al: 39%, and Cu: 4%, whereas, the certified concentration of Devarda’s alloy was 50% for Zn, 45% for Al, and 5% for Cu. These measured results reveal that the elemental concentration utilizing CF-LIBS shows a reasonable agreement with standard estimates illustrated by the manufacturer. This study further suggests that the CF-LIBS technique opens up an opportunity for engineering and industrial usage of LIBS where a quantifiable study of the substance is exceedingly advantageous.

A CuZn-BTC derived stable Cu/ZnO@SiO2 catalyst for ethanol dehydrogenation

Cu-based catalysts play pivotal role in many industrial processes, however, its application under high temperature is restricted due to the low Tammann temperature of Cu. Improving the stability and activity of Cu-based catalysts at high temperature is a challenge. In this work, a stable Cu/ZnO@SiO2 catalyst was prepared, in which silicon was introduced into CuZn-BTC precursor via a steam-assisted hydrolysis method before calcination and reduction. Characterizations found that Cu/ZnO@SiO2 catalyst prepared via above strategy possesses increased surface area, more exposed active sites and excellent stability for ethanol dehydrogenation than Cu/ZnO (prepared from CuZn-BTC without SiO2). It was confirmed that the space-time yield of acetaldehyde reached 9.0 g-acetaldehyde/g-cat/h, and Cu/ZnO@SiO2 could maintain its activity within 200 h at 350 °C due to the ZnO decorated Cu particles (Cu/ZnO) were encapsulated in the octahedral shaped SiO2 hollow.

In-situ X-ray diffraction annealing study of electroplated and sputtered Cu-In-Ga precursors for application to sequential Cu(In,Ga)Se2 processes

• A mechanism is proposed to explain the as-deposited morphology of the film. • The shelf time has a strong impact on the phases present in the precursor. • Annealing above 310 °C erases the sample's history and yields consistent phases. • Between 310 °C and 520 °C, only Cu 9 (Ga,In) 4 and Cu 16 (Ga,In) 9 found in Cu-In-Ga. • The implications for high quality CuInGaSe 2 manufacturing are discussed. We study by in-situ X-ray diffraction (XRD) in a unique, custom-made furnace mimicking an industrial setup, the effect of pre-annealing on electroplated and sputtered thin films of Cu-In-Ga, as precursor material for Cu(In,Ga)(S,Se) 2 (CIGS)-based solar cells. In the first part of the paper, the properties of the as-deposited precursors are investigated. We propose a mechanism to explain how indium, despite being deposited before gallium, systematically ends up on top of the stack. The shelf time at room temperature is also shown to strongly affect the metallic phases present in the precursor, unlike sputtered precursors where only minor changes can be observed. These results are then used as input for the second part of the paper. In the second part, pre-annealing experiments up to 550 °C are carried out on the electroplated and sputtered precursors at atmospheric pressure in an inert N 2 atmosphere and analysed by in-situ XRD. We find that above the decomposition temperature of Cu 11 In 9 (310 °C) and below around 520 °C, mainly Cu 9 (In,Ga) 4 is left in all precursors, regardless of the phases initially present at room temperature or whether the samples were electroplated or sputtered. We validate these findings for a fast heating ramp to 350 °C, followed by a dwell, as is commonly applied in many CIGS fabrication processes. The implications of these results to high quality CIGS manufacturing are then discussed.

Insights into a New Formation Mechanism of Robust Cu/SiO2 Catalysts for Low-Temperature Dimethyl Oxalate Hydrogenation Induced by a Chelating Ligand of EDTA

The Cu/SiO2 catalyst has been widely used in dimethyl oxalate (DMO) hydrogenation due to its low cost and high efficiency. However, the reaction temperature of DMO hydrogenation is higher than the Hüttig temperature of Cu, and the smaller Cu particles are easier to agglomerate. Therefore, there is much interest in constructing a catalyst with a small particle size and strong stability. In the present work, the effect of introducing EDTA on Cu/SiO2 catalysts is systematically investigated. It not only was beneficial to form smaller copper nanoparticles (CuNPs) but also to enhance the stability of Cu species by introducing a suitable amount of EDTA. Furthermore, the surface Cu species were more evenly dispersed, and the number of active sites was increased with the introduction of EDTA; subsequently, the synergistic effect between Cu+ and Cu0 was enhanced. The best performance of 0.08E-Cu/SiO2 had been achieved in the DMO hydrogenation to ethylene glycol (EG), and the DMO conversion and EG selectivity reached 99.9% and 97.7%, respectively. Above all, the 0.08E-Cu/SiO2 catalyst exhibited a high level of stability during the 1200 h life test at 180 °C.

Comparison of Optimum Zno:Al Sputter-Deposition Temperature for Cu(In,Ga)Se2 Photovoltaic Absorbers Prepared by Two Conventional Methods: Elemental Co-Evaporation and Selenization of Sputtered Metal Precursor

Comparison of Optimum Zno:Al Sputter-Deposition Temperature for Cu(In,Ga)Se2 Photovoltaic Absorbers Prepared by Two Conventional Methods: Elemental Co-Evaporation and Selenization of Sputtered Metal Precursor

Electrochemically Converting Liquid Cu2S‐Sb2S3 to Liquid Cu2Sb and Sulfur in Molten Salt at 730 °C

AbstractConventional sulfide metallurgy suffers from SOx gas emission and high energy consumption, owing to the multiple‐step extraction processes and high temperatures that are above the melting point of the extracted metals. Herein, liquid Cu2Sb alloy can be directly electrochemically extracted from the liquid Sb2S3‐Cu2S with no sulfide oxides emission in eutectic NaCl‐KCl molten electrolyte at 730 °C. The use of Sb2S3 decreases the melting point of Cu2S and the Sb decreases the melting temperature of Cu. The Sb2S3‐Cu2S mixture experiences three stages in the electrochemical desulfurization process: the insertion of Na+ into liquid sulfides, the removal of S2− and metallization, and finally the formation of uniform liquid Cu2Sb alloy. The Sb2S3‐Cu2S can be completely electro‐converted into Cu2Sb at 2.6 V for 6 hours. This study provides a straightforward and environmentally friendly route to electro‐synthesize liquid alloys from their molten sulfide minerals.

High H2 selectivity with low coke formation for methanol steam reforming over Cu/Y1.5Ce0.84Ru0.04O4 catalyst in a microchannel plate reactor

The synthesized novel metal oxides YxCeyRuzO4 (x = 1.5, y = 0.84, z = 0.04) which was produced by the sol-gel method was used as a support for Cu active metal on the surface of a microchannel plate reactor in the methanol steam reforming (MSR) process. The prepared catalysts were characterized by X-ray powder diffraction (XRD), BET surface area analysis (SBET), energy-dispersive X-ray analysis (EDX), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), temperature-programmed desorption (NH3-TPD), and temperature-programmed reduction (H2-TPR). High methanol conversion (99.5%) and H2 selectivity (98.7%) and low CO selectivity (1.4%) were achieved for Cu/YxCeyRuzO4 coated microchannel reactor at 250 °C. FE-SEM images and TGA curve of the spent catalyst displayed no coke formation on the surface of the catalyst after 32 h on stream at 300 °C. The low reduction temperature of Cu, high BET surface area, and high pore volume of the catalyst are considered imperative factors that cause a better dispersion of copper on the Y1.5Ce0.84Ru0.04O4 support.

Equation to determine the sizes of various light and heavy metallic nanoparticles prepared by pulsed wire discharge

By theoretically considering the critical size during homogeneous nucleation and the atomic mass of different metals, the equation to determine the sizes of nanoparticles prepared by pulsed wire discharge (PWD) is revisited. The new equation is successful at predicting the sizes of Mg particles, for which submicrometer particles were previously reported to be prepared by PWD, even though their sizes were substantially larger than those of nanoparticles such as Cu, Ni, Ag, or Pd prepared by PWD. The temperature of the cross section of the plasma/vapor cloud at the midpoint of the wire when the plasma/vapor expansion attained its maximum volume was estimated to be approximately 0.7 times the boiling temperature of Mg and 0.56 times the boiling temperature of Cu, Ni, Ag, and Pd. These estimated temperatures are assumed to be nucleation temperature and can be predicted by the latent heat of vaporization. The critical sizes of the nanoparticles at these temperatures were calculated, which complemented the previously proposed equation for the determination of particle size by Tokoi et al. [Jpn. J. Appl. Phys. 52(5R), 055001 (2013)]. The estimated temperature T during this time was verified by investigating the temporal evolution of the temperature along the radial axis using conventional hydrodynamic equations. Mg and Cu wires were also experimentally discharged for comparison of the plasma/vapor cloud conditions during the time of interest using a high-speed camera. The consistency of the high-speed photographs with the simulation results, along with the validity for different nanoparticles prepared by PWD, confirmed the feasibility of the revisited equation.

전차선로 해빙시스템을 위한 발열시험을 통한 전차선 온도상승 특성평가

This paper analyzes the temperature rising characteristics of the deicing catenary system in winter. For the composition of the deicing system, the deicing system is constructed according to the combination of various trolley wires and messenger wires applied at Korea. To compare of temperature rising characteristics, the current distribution ratio between trolley wire and messenger wire are measured and the wire temperature is measured according to the deicing current using a catenary heating test device. In case of current distribution ratio test, the current distribution ratio is measured in 82.1%: 18.9% similar to the theoretical ratio in DC supplying. As a result of temperature rising test, the temperature of Cu 150 ㎟ is increased by 1.26 °C/m at a wind speed of 0.5 m/s and 0.92 °C/m at 2.0 m/s when supplying DC 350 A, And in case of Bz 65 ㎟, when DC 95 A is supplied, the temperature rose at 0.74° C/m at 0.5 m/s, and 0.56 °C/m at 2.0 m/s. In the comparison between the theoretical equation and test result, the difference is at most 0.7 ℃. Therefore, it is confirmed that it would be appropriate to use the theoretical equation in the design of the deicing system.

Adsorption properties of poly(NIPAM-co-AA) immobilized on silica-coated magnetite nanoparticles prepared with different acrylic acid content for various heavy metal ions

Recyclable thermoresponsive heavy metal adsorbents, poly(NIPAM-co-AA) immobilized on silica-coated magnetite nanoparticle (MNP) were prepared by changing the weight ratio between N-isopropylacrylamide (NIPAM) and acrylic acid (AA) monomer and employed for heavy metal ion recovery. The results showed that the adsorbent with the smallest AA amount of 28 mol% in the copolymer exhibited both the highest immobilized copolymer amount of 0.489 g-copolymer/g-MNP and Cu(II) adsorption capacity of 0.511 mol/g-MNP. The result of competitive adsorption using Cu(II), Co(II), Mn(II) and Ni(II) showed that the adsorbent had significant selectivity for Cu(II). Cu(II) recovery from the saturated adsorbent was achieved by merely changing the solution temperature from 50 to 10 °C without using acidic solution, and no deterioration of Cu(II) recovery performance was observed in several cycles. The adsorbent achieved a comparable maximum adsorbed amount with a higher desorption ratio by temperature swing with shorter operation time compared to the other thermoresponsive hydrogel adsorbents. In addition to an isothermal bath heating, induction heating of MNP was applied to control the solution temperature for Cu(II) recovery. The results showed that essentially the same Cu(II) recovery property with shorter recovery time was obtained using the induction heating compared to the isothermal bath heating.

Ferromagnetism With High Curie Temperature of Cu Doped LiMgN New Dilute Magnetic Semiconductors

New diluted magnetic semiconductors represented by Li(Zn,Mn)As with decoupled charge and spin doping have received much attention due to their potential applications for spintronics. However, their low Curie temperature seriously restricts the wide application of these spintronic devices. In this work, the electronic structures, ferromagnetic properties, formation energy, and Curie temperature of Cu doped LiMgN and the corresponding Li deficient system are calculated by using the first principles method based on density functional theory, combined with Heisenberg model in the Mean-Field Approximation. We find that the Cu doped systems have high temperature ferromagnetism, and the highest Curie temperature is up to 573K, much higher than the room temperature. Li(Mg0.875Cu0.125)N is a half metallic ferromagnet and its net magnetic moments are 2.0 μв. When Li is deficient, the half metallic ferromagnetism becomes stronger, the magnetic moments increase to 3.0 μв. The bonding and differential charge density indicate that the half metallic ferromagnetism can be mainly attributed to the strong hybridization between N 2p and doped Cu 3d orbitals. The results show that Cu doped LiMgN is a kind of ideal new dilute magnetic semiconductor that will benefit potential spintronics applications.