Ag-Cu Alloy Research Articles

On the role of structure-dynamic relationship in determining the excess entropy of mixing and chemical ordering in binary square-well liquid alloys

Using statistical mechanical model with square-well (SW) interatomic potential within the frame work of mean spherical approximation, we determine the composition dependent microscopic correlation functions, interdiffusion coefficients, surface tension and chemical ordering in Ag-Cu melts. Further Dzugutov universal scaling law of normalized diffusion is verified with SW potential in binary mixtures. We find that the excess entropy scaling law is valid for SW binary melts. The partial and total structure factors in the attractive and repulsive regions of the interacting potential are evaluated and then Fourier transformed to get partial and total radial distribution functions. A good agreement between theoretical and experimental values for total structure factor and the reduced radial distribution function are observed, which consolidates our model calculations. The well-known Bhatia-Thornton correlation functions are also computed for Ag-Cu melts. The concentration-concentration correlations in the long wavelength limit in liquid Ag-Cu alloys have been analytically derived through the long wavelength limit of partial correlation functions and apply it to demonstrate the chemical ordering and interdiffusion coefficients in binary liquid alloys. We also investigate the concentration dependent viscosity coefficients and surface tension using the computed diffusion data in these alloys. Our computed results for structure, transport and surface properties of liquid Ag-Cu alloys obtained with square-well interatomic interaction are fully consistent with their corresponding experimental values.

Nanoporous Copper-Silver Alloys by Additive-Controlled Electrodeposition for the Selective Electroreduction of CO2 to Ethylene and Ethanol.

Electrodeposition of CuAg alloy films from plating baths containing 3,5-diamino-1,2,4-triazole (DAT) as an inhibitor yields high surface area catalysts for the active and selective electroreduction of CO2 to multicarbon hydrocarbons and oxygenates. EXAFS shows the co-deposited alloy film to be homogeneously mixed. The alloy film containing 6% Ag exhibits the best CO2 electroreduction performance, with the Faradaic efficiency for C2H4 and C2H5OH production reaching nearly 60 and 25%, respectively, at a cathode potential of just -0.7 V vs RHE and a total current density of ∼ - 300 mA/cm2. Such high levels of selectivity at high activity and low applied potential are the highest reported to date. In situ Raman and electroanalysis studies suggest the origin of the high selectivity toward C2 products to be a combined effect of the enhanced stabilization of the Cu2O overlayer and the optimal availability of the CO intermediate due to the Ag incorporated in the alloy.

An electroplated copper–silver alloy as antibacterial coating on stainless steel

Transfer and growth of pathogenic microorganisms must be prevented in many areas such as the clinical sector. One element of transfer is the adhesion of pathogens to different surfaces and the purpose of the present study was to develop and investigate the antibacterial efficacy of stainless steel electroplated with a copper-silver alloy with the aim of developing antibacterial surfaces for the medical and health care sector. The microstructural characterization showed a porous microstructure of electroplated copper-silver coating and a homogeneous alloy with presence of interstitial silver. The copper-silver alloy coating showed active corrosion behavior in chloride-containing environments. ICP-MS measurements revealed a selective and localized dissolution of copper ions in wet conditions due to its galvanic coupling with silver. No live bacteria adhered to the copper-silver surfaces when exposed to suspensions of S. aureus and E. coli at a level of 108 CFU/ml whereas 104 CFU/cm2 adhered after 24 h on the stainless steel controls. In addition, the Cu-Ag alloy caused a significant reduction of bacteria in the suspensions. The coating was superior in its antibacterial activity as compared to pure copper and silver electroplated surfaces. Therefore, the results showed that the electroplated copper-silver coating represents an effective and potentially economically feasible way of limiting surface spreading of pathogens.

Microstructural Characterization of Gas Atomized Copper-Iron Alloys with Composition and Powder Size

Cu-Fe alloys (CFAs) are much anticipated for use in electrical contacts, magnetic recorders, and sensors. The low cost of Fe has inspired the investigation of these alloys as possible replacements for high-cost Cu-Nb and Cu-Ag alloys. Here, alloys of Cu and Fe having compositions of Cu100-xFex (x = 10, 30, and 50 wt.%) are prepared by gas atomization and characterized microstructurally and structurally based on composition and powder size with scanning electron microscopy (SEM) and X-ray diffraction (XRD). Grain sizes and Fe-rich particle sizes are measured and relationships among composition, powder size, and grain size are established. Same-sized powders of different compositions yield different microstructures, as do differently sized powders of equal composition. No atomic-level alloying is observed in the CFAs under the experimental conditions.

Spinodal Decomposition in Nanoparticles - Experiments and Simulation

For revealing internal atomic processes in bimetallic nanoparticles, individual hemispherical Ag-Cu alloy particles were grown by direct current (DC) magnetron sputtering. Phase separation of particles was found to be size- and composition-dependent. Particles smaller than 5 nm in diameter remained as a solid solution of the components for all tested compositions (15-80 at.% Ag). At 15 and 30 at.% Ag compositions phase separation was observed only for particles above 5 nm in diameter. Computer simulations by Stochastic Kinetic Mean Field model reproduced the size-dependence of the decomposition and the internal structure of two-phase particles. Theoretical explanation is given for the composition dependence of the phase separation tendency.

Tuning local surface plasmon resonance of silver and photoluminescence intensity enhancement by adding copper

In order to match the local surface plasmon resonance (LSPR) frequency of Ag with the frequency of light that needs enhancement, the relationship between the free carrier concentration and LSPR frequency must be considered in order to design noble alloy nanoparticles (NPs) to substitute for pure Ag. In this study, Ag, Cu, and Ag-Cu continuous films were prepared by magnetron sputtering to investigate the relationship between the free carrier concentration and LSPR wavelength, which were tested with a Hall effect detector and ultraviolet-visible spectrophotometer, respectively. Ag and Ag-Cu NP films were deposited by short-time magnetron sputtering on an organic-YAG:Ce3+ substrate to test and compare their effects on the photoluminescence (PL) intensity. The thickness of the metal films was determined using an optical thin film analysis system. The morphology was observed for the continuous and NP films by scanning electron microscopy. Compared with the pure Ag films, the Ag-Cu films had a lower free carrier concentration and longer peak wavelength, which was closer to the emission wavelength of YAG:Ce3+. The enhancement ratio for the PL intensity reached a maximum of 1.16 with the Ag NP films. By contrast, for the Ag-Cu NP films with a shorter deposition time, the PL enhancement ratio reached 1.125, where the optimal ratio of Ag to Cu for the product of sputtering power and time was 2:1. The addition of Cu to Ag is beneficial for industrial production because the cost of the materials and the preparation time for Ag-Cu alloy NP films are more than 50% lower compared with pure Ag NP films.

Phase Coexistence of Multiple Copper Oxides on AgCu Catalysts during Ethylene Epoxidation

Alloy catalysts under reaction conditions are complex entities. In oxidizing atmospheres, multiple phases can coexist on a catalyst’s surface as a result of phase segregation and preferential oxidation. Such a scenario can result in unusual substoichiometric and metastable phases that could play important roles in catalytic processes. For instance, AgCu alloys—known to exhibit enhanced epoxide selectivity in partial oxidation of ethylene—form an oxide-like surface structure under reaction conditions. Under these conditions, copper oxides are stable, while silver oxides are not. Consequently, copper segregates to the alloy’s surface and forms an oxide overlayer. Little is known about the structure or function of such overlayers, and it is unknown whether they play an active role in the catalyst’s enhanced selectivity. In order to develop a clearer picture of such catalysts, the current work utilizes several in situ spectroscopic and microscopic techniques to examine the copper oxide phases that form when AgCu is exposed to epoxidation conditions. It is found that several forms of oxidic Cu coexist simultaneously on the active catalyst’s surface, namely, CuO, Cu2O, and some previously unreported form of oxidized Cu, referred to here as CuxOy. Online product analysis, performed during the in situ spectroscopic measurements, shows that increased epoxide selectivity is correlated with the presence of mixed copper oxidation states and the presence of the CuxOy species. These results support previous theoretical predictions that oxidic copper overlayers on silver play an active role in epoxidation. These results furthermore emphasize the need for in situ spectromicroscopic methods to understand the complexity of alloy catalysts.

Experimental characterisation of a CuAg alloy for thermo‐mechanical applications. Part 1: Identifying parameters of non‐linear plasticity models

AbstractDespite the wide use of copper alloys in thermo‐mechanical applications, there is little data on their cyclic plasticity behaviour, particularly for CuAg alloys. This prevents the behaviour of the materials from being correctly described in numerical simulations for design purposes. In this work CuAg0.1 alloy used for thermo‐mechanical applications was tested by strain‐controlled cyclic loading at 3 different temperatures (room temperature, 250°C, 300°C). In each test, stress‐strain cycles were recorded until the alloy had completely stabilised. These cycles were then used to identify material parameters of non‐linear kinematic and isotropic models. The focus was on plasticity models (Armstrong‐Frederick, Chaboche, Voce) that are usually implemented in commercial finite element codes. Simulated cyclic responses with the identified material models were compared with experiments and showed a good agreement. The identified material parameters for the CuAg alloy under investigation can be used directly in finite element models for cyclic plasticity simulations, thus enabling a durability analysis of components under thermo‐mechanical loads to be performed, particularly in the field of steel‐making plants.

Effects of nanocrystalline microstructure on the dry sliding wear behavior of a Cu-10 at% Ag-10 at% W ternary alloy against stainless steel

To explore the W nanoparticles effects on the subsurface microstructural self-organization of Cu-Ag two-phase alloys and the resulting wear performance, we have fabricated bulk nanostructured Cu-10 at% Ag-10 at% W ternary alloys by high energy ball milling and warm pressing. During ball milling, Ag is dissolved into the Cu matrix but W remains immiscible. Compaction of the powders into bulk at 300 °C leads to the Ag precipitation. The as-pressed Cu-10 at% Ag-10 at% W ternary alloy has Ag-rich precipitates size (dAg) of 22 nm and W particles size (dw) of 26 nm. Further annealing at 600 °C for 1 h only increases dAg and dw to 52 nm and 41 nm, respectively. The fabricated Cu-10 at% Ag-10 at% W ternary alloys thus demonstrate enhanced coarsening resistance. The two alloys were then subjected to dry sliding wear against stainless steel disks. It is found that the initial length scale of Ag-rich precipitates and W particles has a profound influence on the microstructure evolution during wear and accordingly on the wear performance. For the as-pressed sample with small dAg and dW, severe plastic deformation (SPD) by wear forced the formation of Cu-Ag homogeneous solid solution, leading to low wear resistance. In contrast, for the annealed one with relatively large dAg and dW, the Cu, Ag and W three phases co-existed but the Ag-rich precipitates were transformed into wavy nanolayers, providing enhanced wear resistance. Compared with Cu-Ag alloys subjected to sliding wear, the presence of W nanoparticles was found to hinder the formation of self-organized nanolayered structure and leads to a small deformation depth. The obtained results provide deep insights into the plastic deformation mechanisms in ternary alloys and the design of wear resistant engineering materials.

Novel Ag-Cu bimetallic alloy decorated near-infrared responsive three-dimensional rod-like architectures for efficient photocatalytic water purification

In this paper, novel silver-copper bimetallic alloy (Ag-Cu) nanoparticles (NPs) decorated β-NaYF4: Yb3+, Tm3+@TiO2 (“@” means TiO2 supported on NaYF4: Yb3+, Tm3+, marked as NYFT) micro-rods were successfully synthesized through a surfactant-assistant sol–gel method and H2 reduction process for the first time. In NYFT@Ag-Cu composite, efficient energy transfer from β-NaYF4: Yb3+, Tm3+ (NYF) to TiO2 and metal NPs was confirmed. Under near-infrared (NIR) light irradiation, Ag-Cu alloy supported NYFT exhibited significantly enhanced photocatalytic activity in comparison with other samples, and water disinfection involving 100% inactivation of bacteria was realized within 8 h. The strengthened photocatalytic activity was assigned to the synergistic effect of up-conversion (UC) material and alloy NPs. Some reasons for the improved photocatalytic activity were systematically investigated and a probable mechanism for NIR-responsive photocatalysis was elucidated.

Experimental characterisation of a CuAg alloy for thermo‐mechanical applications. Part 2: Design strain‐life curves estimated via statistical analysis

AbstractStrain‐life fatigue data on copper alloys, especially type CuAg, are seldom available in the literature. This work fills this gap by estimating the strain‐life curves of a CuAg alloy used for thermo‐mechanical applications, from isothermal low‐cycle fatigue tests at 3 temperatures (room temperature, 250°C, 300°C). Regression analysis is used to estimate the median fatigue curves at 50% survival probability. The comparison of median curves with the Universal Slopes Equation model, calibrated on monotonic tensile properties, shows a fairly good agreement. Design strain‐life curves with a lower failure probability and given confidence are estimated by several approximate statistical methods (“Equivalent Prediction Interval,” univariate tolerance interval, Owen's tolerance interval for regression). When higher survival probabilities are considered, the results show a marked decrease in the allowable design strain at a prescribed fatigue life. The suggested procedure thus improves the durability analysis of components loaded thermo‐mechanically.

СТРУКТУРНЫЕ ОСОБЕННОСТИ СПЛАВОВ CU-AG, ПОЛУЧЕННЫХ МЕХАНОСПЛАВЛЕНИЕМ ХОЛОДНОЙ И КРИОГЕННОЙ МЕГАПЛАСТИЧЕСКОЙ ДЕФОРМАЦИЕЙ

СТРУКТУРНЫЕ ОСОБЕННОСТИ СПЛАВОВ CU-AG, ПОЛУЧЕННЫХ МЕХАНОСПЛАВЛЕНИЕМ ХОЛОДНОЙ И КРИОГЕННОЙ МЕГАПЛАСТИЧЕСКОЙ ДЕФОРМАЦИЕЙ

Experimental characterization of a CuAg alloy for thermo-mechanical applications: non-linear plasticity models and low-cycle fatigue curves

The cyclic response and low-cycle fatigue strength of a CuAg0.1 alloy for thermo-mechanical applications are investigated by isothermal strain-controlled fatigue tests at three temperature levels (room temperature, 250°C, 300°C). Both cyclic and stabilized stress-strain responses are used for identifying the material parameters of non-linear kinematic (Armstrong-Frederick, Chaboche) and isotropic models. The identified material parameters are used in numerically simulated cycles, which are successfully compared to experiments. Linear regression analysis of experimental fatigue data allows the “mean” low-cycle fatigue curves to be estimated. Approximate statistical methods are finally adopted to evaluate the design low-cycle fatigue curves at prescribed failure probability and confidence levels.

Synergistic eminently active catalytic and recyclable Ag, Cu and Ag-Cu alloy nanoparticles supported on TiO2 for sustainable and cleaner environmental applications: A phytogenic mediated synthesis

Ag-Cu monometallic and bimetallic nanoparticles were prepared directly using aqueous extract of Walsura trifoliata supported on TiO2. The extract helps in the in situ immobilization of Ag, Cu and Ag-Cu alloy nanoparticles with face-centered cubic structure using phytochemical compounds as template and reducing agent at ambient conditions. The aqueous extract of W. trifoliata flower acts as reducing, binding, dispersion agent and plays a major role in the synthesis of the nanocomposites which was confirmed using GC-MS. The nanocomposite were characterized using UV–Vis, FTIR, XRD, TEM, SAED, EDS, and Raman Spectra techniques. The efficiency of prepared nanocomposite on the catalytic activity for the reduction and degradation of 4-Nitrophenol (4-NP), Methyl orange (MO), and Rhodamine B (Rh B) with sodium borohydride (NaBH4) were investigated in detail. The Ag-Cu/TiO2 bimetal nanocomposite exhibit very high activity for the degradation of dyes, confirmed using UV–Vis and HPLC analysis. In addition, Ag/TiO2, Cu/TiO2 and Ag-Cu/TiO2 nanocomposites exhibit good reusability with 100% conversion efficiency of 4-NP, MO and Rh B up to 6 successive cycles. The phytogenic mediated synthesis of metal nanocatalyst supported on TiO2 makes it an ideal platform for heterogeneous catalytic process and for potential application in a wide range of fields.

Vacuum brazing of cubic boron nitride to medium carbon steel with Zr added passive and Ti activated eutectic Ag-Cu alloys

Active element like Ti is usually added to Ag-Cu passive alloy to braze cubic boron nitride (cBN) ceramic particles with steel substrate under high vacuum. Current work focusses on another group-IV element Zr, having more negative Gibbs free energy than Ti, concerning its reaction capability with cBN. In the present study, its effectiveness as an additive to the 72Ag28Cu alloy in brazing of cBN has been investigated. Zr is added to both passive and Ti-activated Ag-Cu alloys. Interestingly, the addition of 2wt% Zr to the composition of eutectic alloy fails to braze cBN, unlike the addition of 2wt% Ti. The underlying science is critically investigated. A new formulation of the alloy with the composition of (72Ag28Cu)-4Zr-4Ti alloy is found to be a beneficial alternative. Wetting of this new alloy on cBN is appreciable and simultaneously an additional benefit of 50% increase in wear resistance is achieved, compared to the (72Ag28Cu)-2Ti alloy. A significantly hard new intermetallic phase, AgCu4Zr is detected in the microstructure which contributes to the enhancement of wear resistance of the new alloy. The joint strength thus achieved in brazing cBN with medium carbon steel using (72Ag28Cu)-2Ti and (72Ag28Cu)-4Zr-4Ti alloys is also compared but found to be compromised in case of the later. The results are analyzed in the light of microstructure, alloy-cBN interfacial chemistry and interfacial fracture under load.

Influences of Ag addition to Sn-58Bi solder on SnBi/Cu interfacial reaction

In this study, the influences of Ag addition to Sn-58Bi solder on SnBi/Cu interfacial reaction and fracture behavior of the aged SnBiAg/Cu solder joints were investigated. The results reveal that the Ag element in the solder can diffuse into the Cu substrate during the soldering and aging process, forming a Cu-Ag alloy layer around the joint interface. The Bi segregation was not observed at the aged SnBiAg/Cu interface, and the embrittlement will not occur at the aged SnBiAg/Cu solder joints once the Bi segregation was restrained.

Synthesis of Cu–Ag nanoparticles by biological method

ABSTRACTIn this research, we reported an environment friendly technique for the synthesis of Cu–Ag nanoparticles using the culture supernatant of Rhodopseudomonas capsulata. Aqueous solutions of Cu2+ and Ag+ ions were treated with the culture supernatant of R. capsulata for the formation of Cu–Ag alloy nanoparticles. The formation of the metal nanoparticles was characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The UV-Visible spectra of Cu–Ag nanoparticles showed a surface plasmon resonance peak at 462 nm. It was found that Cu-Ag alloy nanoparticles are synthesized in a size range between 4–15 nm. In addition, TEM revealed the spherical shape of Cu-Ag nanoparticles. The process of reduction is extracellular, which makes it an easier method for the synthesis of Cu-Ag alloy nanoparticles.

Investigation of Origin of Attached Cu-Ag Droplets to Solid Particles During High-Temperature Slag/Copper/Spinel Interactions

This study investigates the origin of mechanically entrained metal droplets in liquid slag due to their interaction with solid spinel particles. Two possible mechanisms were proposed previously: separately formed droplets and spinel particles get attached to each other due to agitation of the slag and metal phases; or the spinel particles form by a chemical reaction together with a new droplet or alongside a droplet that was already present in the system. In this study, an inert tracer element was added to the metallic phase in adapted sessile drop experiments. For this purpose, Cu-Ag alloys, with various Ag-contents, were produced. The results showed that the small entrained metal droplets within the slag droplet contained Ag, but in very low amounts with respect to the amount of Ag in the Cu-Ag alloy. This indicates that the entrained metal droplets are formed due to a sequential combination of the two origins: first, very small metal droplets are dispersed in the slag drop, due to the emulsification process. Then, these metal droplets are nucleation sites for the Cu-spinel reactive formation.

New version of Kurnakov’s law about relationship between properties of binary alloys and phase diagrams balance

The representation of the state diagram as a concentration dependence of qualitative changes in crystallization (recrystallization) intervals is introduced for the first time. This makes it possible to connect the phase diagram with inexplicable properties of the phase composition or the structure of the anomaly in the properties of Zn-Cd, Sn-Pb, Cu-Ag, Al-Si, and Fe-C double alloys. A new version of Kurnakov’s law is presented which allows associating the anomalies of binary alloy properties with qualitative changes in crystallization intervals.

Influence of cerium on solidification, recrystallization and strengthening of Cu-Ag alloys

Cu-Ag-RE alloys with different Ce contents were prepared by vacuum melting, and microstructure evolution and mechanical properties of Cu-Ag-Ce alloys were investigated by optical microscopy, scanning electronic microscopy with electron back-scattered diffraction and tensile test. The results indicated that a columnar to equiaxed transition in cast Cu-Ag-RE alloys was observed due to Ce addition and area of the region with equiaxed grains enlarged with increasing Ce content. Cold-rolled Cu-Ag-RE alloys in annealed condition exhibited a partially or fully recrystallized grain structure depending on the concentration of Ce. The average grain size decreased and texture components changed with increasing Ce content. The main brass-type texture component changed to be copper-type as the Ce content increased from 0.05 wt.% to 1.0 wt.%. The Cu-Ag-RE alloy with 0.2 wt.% Ce showed maximum ultimate tensile strength, while the sample with 1.0 wt.% Ce showed a better comprehensive mechanical property.