Region Of Cu Research Articles

Analysis of indentation stress-strain response of copper by in-situ observation using optical indentation microscopy

In this study, deformation behavior in a limited region of Cu with various average grain sizes was investigated by optical indentation microscopy (OIM), a novel in-situ indentation method. The relationship between the macroscopic yield stresses estimated from uniaxial compressive tests and the indentation yield stresses in the limited region estimated by OIM followed an empirical model. The yield stresses in the limited region estimated by OIM depend on the grain size, and they satisfied the Hall-Petch relationship as well as the macroscopic yield stress. The macroscopic yield stresses predicted from the indentation yield stresses were consistent with the experimentally estimated values. Therefore, it is concluded that it is possible to estimate the macroscopic yield stress from the deformation behavior of the limited region analyzed by OIM.

CALPHAD-guided alloy design of Cu–Pb–(X) immiscible alloy with rodlike secondary phases

Novel Cu–24Pb–xAl alloys with dispersed and rodlike Pb-rich secondary phases (PSPs) were designed and prepared with the guidance of CALPHAD. Through primary binary-phase diagram analysis and thermodynamic calculation, Al was proven to be a suitable alloying element in Cu–Pb system to promote the formation of dispersed and rodlike PSPs during solidification by introducing a (L1 + L2 + α-Cu) phase region in Cu–Pb–xAl systems. The Cu–24Pb–xAl (wt-%, x = 0, 2, 4) alloys were then prepared in order to verify the reliability of the alloy design strategy. Cu–24Pb–2Al alloy with rodlike PSPs was successfully designed and prepared. A novel strategy to design Cu–Pb–(X) immiscible alloy with optimised microstructure is thus proposed in this work which can help establish a design criterion for other immiscible alloys.

High load sliding, deformation microstructures, strength, and hardening for cutting and metal forming

The plowing action of ridge and wedge shaped micro asperities under large sliding loads is utilized to induce extremely high hardness and strain levels in the subsurface regions of Cu. A unique apparatus was designed and employed to apply high normal stresses (loads) that ranged herein from 0.4 to 3.7 times the yield stress, at either ambient (293 K) or cryogenic (77 K) temperatures. A steep gradient in the size scale of the induced deformation microstructures is coupled to an unprecedented average size (crystallite) scale of 5 nm that includes a high dislocation density near the surface. This structural size is graded in size from very fine at the surface to large with increasing depth and decreasing strain. Due to these size scales, quantitative and statistical measurements of the subsurface deformation microstructures, as a function of depth, load, and temperature were performed with high resolution transmission, scanning electron, and microprobe microscopy. The observed deformation microstructures follow the principal of grain subdivision creating a hierarchical structure, but with a finer size scale, that is similar to deformation structures developing under different deformation modes. The measured structure parameters include the inverse spacing, 1/DavGNB, of deformation induced boundaries (geometrically necessary boundaries GNBs), that have evolved with increasing strain to have medium to high misorientation angles like grain boundaries, and the dislocation density, ρav, in between the GNBs. Dislocation mechanisms were demonstrated to dominate the subsurface deformation at all size scales based on the high density of dislocations, the average refinement that extends to 5 nm, and universal scaling. Subsurface stress estimates use the measured parameters in a linear addition of the classic Hall-Petch formulation for the barrier strength contribution of 1/DavGNB, plus Taylor forest dislocation hardening for the contribution of ρav. A further unification of these parameters is made since ρav is directly proportional to 1/DavGNB. Flow stress estimates indicate that the nearest subsurface layers are extremely hard, 1.7–2.8 GPa with hardness and subsurface refinement increasing with increasing normal load and decreasing temperature. At the highest load and 77 K, the depth at which large shear strains are observed is increased by a factor of about six, i.e. eighty times the average platen asperity height. A quantitative comparison of friction and deformation energies is made together with the stress and strain estimates. Friction and deformation energies increase with increasing the normal loads. At the same time, coefficients of friction decrease due to the creation of a harder surface at higher loads. Large sliding or rubbing loads are present during cutting and metal forming creating subsurface deformation. These loads largely contribute to high friction forces, and strongly influence surface finishes and subsurface hardness.

WITHDRAWN: High luminescence efficiency of Copper doped Zinc Sulfide (Cu: ZnS) nanoparticles towards LED applications

Abstract The study was focused on to prepare transitions semiconducting material of Cu doped ZnS NPs from various concentrations (2.5, 5.0, 7.5, and 10%) of ZnS nanoparticle through the sol–gel method. The optical, electrical, and morphological properties of synthesized nanoparticles were studied by different categorisation methods such as XRD, FTIR, and EDAX. The crystalline property and phase clarity of the product was investigated by XRD analysis and found that the phase pure cubic structure of ZnS without any secondary phases. The functional property of the product was studied by FTIR analysis. The morphology and chemical composition were examined by microscopic analysis (TEM) and EDAX spectrum, respectively, and found that the typical particle size is around 10 nm and the presence of a meager atomic percentage of Cu. The energy gap of the material is investigated by optical analysis using the Kubelka-Munk function. The energy gap is significantly varied from 2.26 eV to 3.05 eV as rise in Cu dosage from 2.5% to 10%. Photoluminescence analysis reveals that the wide range of tunable release from the blue to green regions of Cu doped ZnS NPs.

NaF/RbF-Treated Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers: Distinct Surface Modifications Caused by Two Different Types of Rubidium Chemistry.

The underlying beneficial mechanism of heavy alkali postdeposition treatment (PDT) of Cu(In,Ga)Se2 thin-film solar cell absorbers that led to new record efficiencies in recent years is studied using photoelectron spectroscopy. Excitation energies between 40.8 eV and 6 keV were used to examine the near-surface region of Cu(In,Ga)Se2 thin-film solar cell absorbers that underwent NaF and combined NaF/RbF PDT. The already Cu-deficient surface region after NaF PDT, which is modeled as a Cu:(In + Ga):Se = 1:5:8 phase, shows further depletion after NaF/RbF PDT and seems to incorporate some Rb. Additionally, we have found strong indications for the NaF/RbF PDT-induced formation of a Rb-In-Se-type compound with a 1:1:2 stoichiometry partially covering the absorber surface. The electronic Cu(In,Ga)Se2 structure is modified due to the RbF treatment, with a pronounced shift in the valence band maximum away from the Fermi level in the immediate vicinity of the surface.

Fingerprint Voltammograms of Copper Single Crystals under Alkaline Conditions: A Fundamental Mechanistic Analysis.

A critical step toward the systematic development of electrocatalysts is the determination of the microscopic structure and processes at the electrified solid/electrolyte interface. The major challenges toward this end for experiment and computations are achieving sufficient cleanliness and modeling the complexity of electrochemical systems, respectively. In this sense, benchmarks of well-defined model systems are sparse. This work presents a rigorous joint experimental-theoretical study on the single-crystal (SC) Cu/aqueous interface. Within typical computational uncertainties, we find quantitative agreement between simulated and experimentally measured voltammograms, which allows us to unequivocally identify the *OH adsorption feature in the fingerprint region of Cu(110), Cu(100), and Cu(111) SCs under alkaline conditions. We find the inclusion of hydrogen evolution reaction kinetics in the theoretical model to be crucial for an accurate steady-state description that gives rise to a negligible H* coverage. A purely thermodynamic description of the H* coverage through a Pourbaix analysis would incorrectly lead to a H* adsorption peak. The presented results establish a fundamental benchmark for all electrochemical applications of Cu.

Visualization of the tensile fracture behaviors at adhesive interfaces between brass and sulfur-containing rubber studied by transmission electron microscopy

Composites of polymers and inorganic materials have recently attracted considerable attention as lightweight tough materials. In this study, we examined the structures and fracture paths at the adhesive interfaces between a sulfur-containing rubber compound and brass formed during vulcanization. Samples consisting of brass fillers dispersed in a rubber matrix were subjected to in situ tensile observations using transmission electron microscopy. Upon uniaxial stretching, fracture occurred between the rubber compound and outermost CuxS layers of the adhesive interface. With prolonged vulcanization, the adhesive interface became broader and depletion regions of Cu and Zn appeared inside the particles, indicating sample degradation, owing to outward diffusion of the metal elements into the rubber compound. Fracture of the degraded rubber composite occurred along the depletion regions. These observations demonstrate that the adhesiveness of brass and rubber composites strongly depends on the interfacial structures.

Near‐Surface [Ga]/([In]+[Ga]) Composition in Cu(In,Ga)Se2 Thin‐Film Solar Cell Absorbers: An Overlooked Material Feature

The chemical and electronic structures in the near‐surface region of Cu(In,Ga)Se2 thin‐film solar cell absorbers are investigated using nondestructive soft and hard X‐ray photoelectron spectroscopy. In addition to a pronounced surface Cu‐depletion, the [Ga]/([In]+[Ga]) composition indicates that the topmost surface is Ga‐poor (or In‐rich). For the studied depth region, common depth profiling techniques generally fail to provide reliable information and, thus, the near‐surface chemical and electronic structure profiles are often overlooked. The relation between the observed near‐surface elemental compositions and the derived electronic properties of the absorber material is discussed. It is found that the surface band gap energy crucially depends on the Cu‐deficiency of the absorber surface and suggests that it is, in this region, only secondarily determined by the [Ga]/([In]+[Ga]) ratio.

Engineered Cu(InGa)Se2 thin films through CaF2 post-deposition treatment for enhancing solar cell performance

It is considered that alkaline elements (such as Na, K, Rb) introduced through post-deposition treatment are able to modify the near-surface region of Cu(InGa)Se2 thin films. However, research on the effects of Ca element on properties of Cu(InGa)Se2 thin films is hardly reported. In this paper, Cu(InGa)Se2 thin films were prepared on quartz glass by e-beam evaporation via two-step process. Study of structural property showed that a certain amount of CaF2 through post-deposition treatment was beneficial to the uniform composition distribution of Cu(InGa)Se2 thin films. Near-surface region of Cu(InGa)Se2 thin films was more Cu-depleted by increasing introduced amount of Ca element. It was inferred that Ca diffused into the Cu(InGa)Se2 thin films substituted the In sites as CaIn so as to increase the carrier concentration. By calculation, the spike barrier of CdS/Cu(InGa)Se2 heterojunction was shown to decrease with increased thickness of CaF2 layers. As a result, Cu(InGa)Se2 solar cell subjected to 20 nm CaF2 post-deposition treatment, which possessed higher fill factor, open circuit voltage and short circuit current density, achieved the optimal power conversion efficiency. An efficiency of Cu(InGa)Se2 solar cell was enhanced by 2.9% after 20 nm CaF2 post-deposition treatment.

Stabilizing the metastable γ phase in Ga2O3 thin films by Cu doping

The metastable cubic γ phase Ga2O3 with a defect spinel structure presents several fascinating properties, which may be a more attractive material than the stable β form. Herein, we found that the metastable γ-Ga2O3 can be stabilized by copper (Cu) doping through a simple operation and low cost method of sol-gel. The γ-Ga2O3 thin films were prepared under the annealing of 700 °C in nitrogen atmosphere for Cu doping. The β phase Ga2O3 ones were obtained at the same condition without the Cu dopant. While the Cu doped γ phase Ga2O3 will transform to β phase for a high annealing temperature above 800 °C. The grain size of Cu doped γ-Ga2O3 and undoped β-Ga2O3 thin films increases with the increase of the annealing temperature. The UV–Vis absorption spectrum of the β-Ga2O3 thin film exhibits a sharp intrinsic absorption edge at ∼250 nm, whilst Cu doped γ-Ga2O3 thin film displays an obvious red-shift. The band gap decreases from 4.90 eV to 4.38 eV for the Cu doping. The photoluminescence intensity at the ultraviolet and blue region of Cu doped γ-Ga2O3 thin films are stronger than undoped β-Ga2O3, which can be attributed to the introduction of more defects such as oxygen vacancies in γ phase by Cu doping.

Non-isothermal Crystallization Kinetics and Isothermal Crystallization Kinetics in Supercooled Liquid Region of Cu–Zr–Al–Y Bulk Metallic Glass

The crystallization kinetics of Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 bulk metallic glasses in non-isothermal and isothermal conditions was studied by differential scanning calorimetry. In the non-isothermal and isothermal modes, the average activation energy of (Cu43Zr48Al9)98Y2 is larger than that of Cu43Zr48Al9, meaning the higher stability against crystallization of (Cu43Zr48Al9)98Y2. In addition, the average activation energies for Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 calculated using Arrhenius equation in isothermal mode are larger than the values calculated by Kissinger–Akahira–Sunose method in non-isothermal mode, indicating that the energy barrier is higher in isothermal mode. The Johnson–Mehl–Avrami model was used to analyze the crystallization kinetics in the non-isothermal and isothermal modes. The Avrami exponent n for Cu43Zr48Al9 is above 2.5, indicating that the crystallization is mainly determined by a diffusion-controlled three-dimensional growth with an increasing nucleation rate, while the Avrami exponent n for (Cu43Zr48Al9)98Y2 is in the range of 1.5–2.5 in the non-isothermal mode, implying that the crystallization is mainly governed by diffusion-controlled three-dimensional growth with decreasing nucleation rate. Finally, the Avrami exponents n for Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 are different in the non-isothermal and isothermal conditions, which imply different nucleation and growth behaviors during the crystallization processes.

Novel heterogeneous photocatalysts prepared with waste wool and Fe3+ or Cu2+ ions for degradation of CI Reactive Red 195: a comparative study

In order to reuse waste wool, two transition metal ions, Fe3+ and Cu2+, were coordinated to with it to prepare a series of metal–wool complexes as new heterogeneous Fenton photocatalysts for the degradation of a typical azo dye, CI Reactive Red 195, in aqueous solution. The effect of the initial metal ion concentration and temperature on the reaction was investigated. Furthermore, the catalytic performance of the resulting metal–wool complexes was evaluated with respect to the dye decoloration efficiency at different pH levels under visible irradiation. The results demonstrated that increasing the initial metal ion concentration and temperature enhanced ion coordination to produce complexes of increased metal content. The obtained Fe–wool showed a higher metal content than the Cu–wool. The light adsorption performance in the UV and visible regions of Cu–Fe–wool is stronger than that of Fe–wool or Cu–wool. Furthermore, Cu–Fe–Wool was found to have a higher catalytic activity than the other two complexes under visible irradiation, especially in the alkaline pH range.

Co diffusion in the near-surface region of Cu

We present our experimental and theoretical study on Co diffusion in the first few atomic layers of Cu(001). While the diffusion of Co atoms in Cu(001) is usually expected to be intense at a temperature $T\ensuremath{\ge}800$ K, in the vicinity of the surface, it is already activated at a considerably lower temperature $T\ensuremath{\sim}650$ K whereas the diffusion in the deep bulk region is still inhibited. This intense near-surface diffusion provides an accumulation of Co atoms in the first six atomic layers upon a single stage Co deposition. The details of the near-surface diffusion are studied by analyzing the distribution of the location depth of the buried single Co atoms. The depth of location of single Co atoms is deduced from scanning tunneling microscopy (STM) data. The subsurface Co atoms induce a perturbation of the electron density of states of the surface which is observable as apparent ringlike ripples in the STM images of the atomically flat Cu surface. The depth of location of the buried Co atoms is determined from the diameter of those rings. The largest amount of Co atoms is found to be in the third layer, emphasizing that the near-surface diffusion should be described by diffusion parameters different from those for bulk diffusion. A model that describes the embedding process of Co atoms into Cu(001) layers is developed. The model assumes Co atoms to diffuse via the vacancy and ring-exchange mechanisms. The energy barriers for the interlayer Co diffusion via those mechanisms are calculated using the nudged elastic band method. The model satisfactorily explains the experimental results. Our study reveals that the energy barriers for Co diffusion in the first five atomic layers of Cu(001) are lower than those in the bulk. This defines the region in which Co diffusion should be considered as a near-surface one.

Effects of the surface sulfurization reactions on the structural and photovoltaic properties of Cu(In,Ga)(Se,S)2 solar cells

The influence of sulfurization treatment in the structural and photovoltaic properties of Cu(In,Ga)(Se,S)2 films was investigated in this study. X-ray diffraction patterns and secondary ion mass spectrometry results revealed that sulfur-rich Cu(In,Ga)(Se,S)2 layers were formed near the surface region of absorber films. Prolonging the duration of sulfurization process increased the amount of sulfur species by replacing the selenium ions of Cu(In,Ga)Se2 films. The photoluminescence spectra indicated a significant reduction of selenium vacancies near surface region of Cu(In,Ga)(Se,S)2 films. The conversion efficiency of fabricated Cu(In,Ga)(Se,S)2 solar cells was increased from 9.81% to 11.63% by sulfurization treatment. In a diode analysis, the annihilation of selenium vacancies and the improved morphology reduced the formation of shunt paths, lowering the diode factor and saturated current. This investigation demonstrates that the controlled surface sulfurization effectively improved the photovoltaic performance of Cu(In,Ga)(Se,S)2 solar cells.

X-Ray Nanotomography of Cu6Sn5 Anode Material for Li-Ion Batteries

In recent years, great attention has been paid to tin as an alternative to graphite as a negative electrode material in Li-ion batteries due to the high theoretical capacity of its fully lithiated phase, Li4.4Sn (994 mAh∙g-1). However, tin suffers from large volume expansion during lithiation and delithiation causing capacity to drop quickly as a function of cycle number. Significant volume expansion of the negative electrode has severe effects that reduce the cycle lifetime of the electrode such as material pulverization, separation from the current collector, and instability of the solid electrolyte interphase. One way to reduce this expansion is to create an inert matrix to help support the Sn during electrochemical cycling such as the use of copper in the form of the intermetallic alloy Cu6Sn5. As the issues stemming from this severe volume expansion all occur on a microstructural level, x-ray nanotomography (XNT) is used to image the anode material at a resolution of 60 nm. XNT provides the opportunity to non-destructively obtain the 3D structure of heterogeneous materials and provide a series of high resolution digital images for microstructural analysis and computational modeling. In this current study, Cu6Sn5 was synthesized by sintering copper and tin in the stoichiometric proportion to form the alloy anode material. XNT measurements were taken of the resulting non-lithiated material at 8.8 KeV over a 180° range of rotation. Single component and mixed samples containing the bronze alloy, Cu, and Sn were imaged. Based on absorption contrast regions of Cu, Sn, and Cu6Sn5 were differentiated throughout multiple samples. The capability to distinguish the different materials within mixed samples suggests that microstructure and composition changes resulting from lithiation and delithiation in Cu6Sn5 can be observed and better understood with 3D x-ray imaging methods. These methods may also be applicable to other intermetallic alloy electrode systems.

ϕmeson production in the forward/backward rapidity region in Cu + Au collisions atsNN=200GeV

The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured $\phi$ meson production and its nuclear modification in asymmetric Cu$+$Au heavy-ion collisions at $\sqrt{s_{NN}}=200$ GeV at both forward Cu-going direction ($1.2<y<2.2$) and backward Au-going direction ($-2.2<y<-1.2$), rapidities. The measurements are performed via the dimuon decay channel and reported as a function of the number of participating nucleons, rapidity, and transverse momentum. In the most central events, 0\%--20\% centrality, the $\phi$ meson yield integrated over $1<p_T<5$ GeV/$c$ prefers a smaller value, which means a larger nuclear modification, in the Cu-going direction compared to the Au-going direction. Additionally, the nuclear-modification factor in Cu$+$Au collisions averaged over all centrality is measured to be similar to the previous PHENIX result in $d$$+$Au collisions for these rapidities.

Using EVT for Geological Anomaly Design and Its Application in Identifying Anomalies in Mining Areas

A geological anomaly is the basis of mineral deposit prediction. Through the study of the knowledge and characteristics of geological anomalies, the category of extreme value theory (EVT) to which a geological anomaly belongs can be determined. Associating the principle of the EVT and ensuring the methods of the shape parameter and scale parameter for the generalized Pareto distribution (GPD), the methods to select the threshold of the GPD can be studied. This paper designs a new algorithm called the EVT model of geological anomaly. These study data on Cu and Au originate from 26 exploration lines of the Jiguanzui Cu-Au mining area in Hubei, China. The proposed EVT model of the geological anomaly is applied to identify anomalies in the Jiguanzui Cu-Au mining area. The results show that the model can effectively identify the geological anomaly region of Cu and Au. The anomaly region of Cu and Au is consistent with the range of ore bodies of actual engineering exploration. Therefore, the EVT model of the geological anomaly can effectively identify anomalies, and it has a high indicating function with respect to ore prospecting.

Mechanism of ferrite grain refinement in the (γ + α) region of weathering steel Cu–P–Cr–Ni–Mo

Abstract

Ultrasonic bonding of Cu/Ni and its thermal reliability

In this study, we ultrasonically bonded Cu and Ni sheets and evaluated the thermal reliability of the joints at 473 K by high-temperature testing. Furthermore, we observed the interfacial microstructures of the joint and evaluated their effects on the bondability of the joint. Cu and Ni sheets were metallurgically bonded under the optimum condition of ultrasonic bonding. Cu base metal strongly deformed compared with deformation of Ni base metal during ultrasonic bonding. The ultrasonically bonded interface of Cu and Ni sheets was composed of bonded region and unbonded region. The bonded region was composed of two types of microstructures. Cu and Ni were locally stirred and an ∼200-nm thickness of solid-soluted region of Cu and Ni atoms was formed in the bonded region. The Cu grains were fine; moreover, the Ni grains became fine from the bonded interface to the Ni side of 1–2 μm. These fine grains can be formed by deformation of bonded base metals during the ultrasonic bonding process, suggesting that plastic deformation was formed from the soft Cu base metal to the hard Ni base metal. The ultrasonically bonded joints showed good thermal reliability at 473 K through the holding time up to 1000 h. Some of the Cu grains became coarse in the Cu base metal. Phase separation of the solid-soluted region of Cu and Ni atoms may occur during the high-temperature test performed at 473 K.

Estimation of the sizes of disordered surface regions of Cu and Ag thin films using the ion transmission method

The dimensions of cluster phases that form on the surfaces of free Cu and Ag films in the case of different irradiation doses are estimated for the first time. It is shown that ion implantation leads to a significant decrease in the number of ions passed through a free film. Under the same conditions of the ion implantation, the concentration of impurity atoms on the surface and their depth-distribution profile for the free film differ noticeably from those for a bulk crystal.