Ag-Cu Alloy Research Articles

Synergistic Effect of Plasma and Laser Processes in Liquid for Alloyed-Nanoparticle Synthesis

Cu-Ag alloy nanoparticles (NPs) have been synthesized from micropowders of pure Cu and Ag using consecutively two non-equilibrium processes based on plasma and lasers in liquids. Plasma process reduces the size of initial micrometric powders down to nanometric size at which the laser fluence is sufficient to melt them, making alloying possible. Measurements at macroscopic (solution absorption), microscopic (scattering of individual NPs) and nanoscopic (electron microscopy) scales confirm alloying of NPs and homogenization in size and composition. This has noticeable effect on the final colloidal solution that absorbs yellow-orange light (550-600 nm) after laser treatment. The possibility to quench the as-formed liquid alloy leads to phase compositions that are not compliant with the phase diagram. With a synthesis rate of 360 mg/h, this process opens up interesting perspectives for non-equilibrium nanometallurgy of functional NPs.

Dramatically Enhanced Combination of Ultimate Tensile Strength and Electric Conductivity of Alloys via Machine Learning Screening

Optimizing two conflicting properties such as mechanical strength and toughness or dielectric constant and breakdown strength of a material has always been a challenge. Here we propose a novel machine learning approach to dramatically enhancing the combined ultimate tensile strength (UTS) and electric conductivity (EC) of alloys by identifying a set of key features through correlation screening, recursive elimination and exhaustive screening of existing datasets. We demonstrate that the key features responsible for solid solution strengthened conductive Copper alloys are absolute electronegativity, core electron distance, and atomic radius, based on which, we discovered a series of new alloying elements that can significantly improve the combined UTS and EC. The predictions are then validated by experimentally fabricating four new Cu-In alloys which could potentially replace the more expensive Cu-Ag alloys currently used in railway wiring. We show that the same set of key features can be generally applicable to designing a broad range of conductive alloys.

The effect of Aluminium addition on the microstructure of lead-free solder alloys: A short review

The ban on using lead in electronic packaging has been taken effect since the year 2006. The alternative to replacing lead (Pb) based solder has been given highly concerns by the electronic industry. Both Sn- Ag-Cu and Sn-Cu solder alloys were considered to be the most acceptable candidates to replace SnPb solder alloy. From the findings, it showed that β-Sn appears as island-liked shape and eutectic phases appear as a darker shade. The grain size is refined significantly after incorporated with a suitable amount of Al. When exorbitant amount of Al addition will cause Al-rich particles, which has high potential to acts as the heterogeneous nucleation site and result in a lower degree of undercooling. The most desired amount of Al addition is between 0.025 - 0.05 wt%. The primary intermetallic compounds found in Sn-based solder alloy are Cu6Sn5 and Ag3Sn. New intermetallic compouds were found after addition of Al, which are Cu-Al and Ag-Al intermetallic. The formation of new intermetallic compounds causes the formation of Cu6Sn5 and Ag3Sn to be suppressed.

High-Performance Ag-Cu Nanoalloy Catalyst for the Selective Catalytic Oxidation of Ammonia.

High-performance Ag-Cu alloy nanoparticles (NPs) were successfully synthesized by a solventless mix-bake-wash method and tested for NH3-SCO. The prepared Ag2Cu1 catalyst with a perfect Ag-Cu alloy structure exhibited better T100 (200 °C, the temperature at which 100% NH3 conversion was obtained), higher reaction rates, and lower Ea compared to that with ordinary bimetallic Ag-Cu (AgCuOx). The characterization data revealed much smaller Ag-Cu alloy nanoparticles of the Ag2Cu1 catalyst and more Ag/Cu metallic species on the surface, which can increase the amount of chemisorbed surface oxygen (Oβ) and enhance NH3 adsorption and activation in the low-temperature range, therefore leading to a much higher NH3-SCO activity. Kinetic studies and density functional theory calculations indicated that Cu decoration at Ag by Ag-Cu alloying could enhance the adsorption/activation of NH3 and O2. It has been found that O2 was more easily transformed from the adsorption state to the transition state than NH3, which enhanced the performance of NH3 oxidation. In addition, the Ag2Cu1 catalyst exhibited excellent durability because of the stabilization of Ag sites by the Ag-Cu alloy structure.

Investigation on Strength, Ductility and Electrical Conductivity of Cu-4Ag Alloy Prepared by Cryorolling and Subsequent Annealing Process

Cu-Ag alloy is widely used as conductive material for high-field pulsed magnets in electrical industry. The cryorolling technique is considered as the most applicable severe plastic deformation technique. Therefore, in this study, cryorolling and subsequent annealing process were used to prepare Cu-4Ag (in wt.%) alloy sheets. The strength, ductility and electrical conductivity of Cu-4Ag alloy sheets were investigated. Microstructure of Cu-4Ag alloy was also studied by OM, SEM, XRD and TEM. As a result, the cryorolling specimens after annealing at temperature of 300 °C display a good combination of tensile strength of 652.2 ± 6.0 MPa, moderate elongation of 12.5 ± 0.7% and electrical conductivity of 80.6 ± 0.2% IACS. This is due to the presence of dislocations, dislocation cells, nanograins and nanotwins in the non-recrystallized regions and fine nanoscaled silver precipitates. Besides, a good ductility is achieved in this condition due to its desirable ductile fracture characteristics.

Enhancement of the thermal conductivity of polypropylene with low loadings of CuAg alloy nanoparticles and graphene nanoplatelets

Isotactic polypropylene (iPP), silver-rich shell CuAg nanoalloys and graphene nanoplatelets (GNPs) were used to prepare thermally conductive binary (iPP/CuAg and iPP/GNPs) and ternary (iPP/CuAg/GNPs) nanocomposites with filler compositions from 0.1 to 5 wt.% through melt processing. All nanocomposites were thermally and electrically characterized. Results showed that both nanoparticles nucleate the crystallization of iPP, shifting the crystallization transition toward higher temperature as compared with that of iPP. The nanoparticles dispersion was not optimum but was enough to make the nanocomposites thermally conductive between 0.65 and 1.56 W m−1 K−1 and more thermally stable (443 °C) than neat iPP (347 °C). For the iPP/CuAg nanocomposites, the increase in the electrical conductivity from 10−15 to 10−3 S m−1 suggests the formation of a percolated network. In contrast, for iPP/GNPs nanocomposites, no improvement in this property was observed. Finally, for iPP/CuAg/GNPs nanocomposites, the measured electrical conductivity (10−15 S m−1) suggests that the polymer-GNP interface is acting as a charge carrier trap. This effect is commonly reported in binary nanocomposites but little or no data exists for ternary NCs.

Modeling the annealing and thermal stability of silver dental amalgam.

Effect of heat treatment on the structure and thermal properties of silver-copper dental amalgam (Ag-Cu/Hg) was investigated by means of Monte Carlo (MC) simulation. Simulated pair correlation functions in the framework of MC algorithm form the basis for a diverse analysis of the amalgam annealed up to 2893K. As heat treatment increases, structural properties remain essentially unchanged up to 1093K, beyond which, the properties are deteriorated. Phase separation in the context of homo-coordination and segregation of Ag-Cu alloy is characterized as the annealing of amalgam alloy is proceeded. Thus, the amalgam alloy could also maintain a microstructural phase and a structural strength around this temperature, consistent with the annealing reported experimentally. These findings provide insights into amalgam industrial technology, setting amalgamation process, Hg release in dental clinics, and basic information appreciated in the dentistry industry and partnership in forensic science. Graphical abstract Thermal stability of the homogeneous amalgam (Ag-Cu/Hg) is studied up to 2893 K where a phase separation and structural alteration is noted above 1093 and Hg phase segregates into a domain different from Ag-Cu alloy domain.

Corrosion study of brazing Cu[sbnd]Ag alloy in the presence of benzotriazole inhibitor

The effect of benzotriazole (BTA) on the corrosion behavior of brazing CuAg alloy in deionized water was investigated using corrosion potential measurements, potentiodynamic polarization and X-ray photoelectron spectroscopy (XPS). Pure Cu, pure Ag and a high Cu alloy were included for comparison. The electrochemical responses show that BTA shifts the corrosion potential of Cu to the noble direction but has the opposite effect for Ag and a mixed behavior for the CuAg alloys. The inhibition efficiency of BTA for Cu and high Cu alloy reached around 95% but was significantly lower for Ag and the brazing CuAg alloy. XPS results show the formation of Cu- and Ag-BTA complexes through the N tail of BTA. The lower inhibition efficiency of Ag and brazing alloy can be attributed to the weak adsorption of BTA on the Ag phase leading to lower corrosion protection of Ag.

Enhanced Light Utilization in Semitransparent Organic Photovoltaics Using an Optical Outcoupling Architecture.

Building-integrated photovoltaics employing transparent photovoltaic cells on window panes provide an opportunity to convert solar energy to electricity rather than generating waste heat. Semitransparent organic photovoltaic cells (ST-OPVs) that utilize a nonfullerene acceptor-based near-infrared (NIR) absorbing ternary cell combined with a thin, semitransparent, high conductivity Cu-Ag alloy electrode are demonstrated. A combination of optical outcoupling and antireflection coatings leads to enhanced visible transmission, while reflecting the NIR back into the cell where it is absorbed. This combination of coatings results in doubling of the light utilization efficiency (LUE), which is equal to the product of the power conversion efficiency (PCE) and the average photopic transparency, compared with a conventional semitransparent cell lacking these coatings. A maximum LUE = 3.56 ± 0.11% is achieved for an ST-OPV with a PCE = 8.0 ± 0.2% at 1 sun, reference AM1.5G spectrum. Moreover, neutral colored ST-OPVs are also demonstrated, with LUE = 2.56 ± 0.2%, along with Commission Internationale d'Eclairage chromaticity coordinates of CIE = (0.337, 0.349) and a color rendering index of CRI = 87.

Electromigration effect upon single- and two-phase Ag-Cu alloy strips: An in situ study

Electromigration (EM) is a major failure mode in electronic interconnections, which is commonly made of Ag, Cu, and their alloys. Herein, a single- and two-phase AgCu alloys were subjected with current density of 4 × 105 A/cm2 for in situ microstructural and crystallographic characterizations. Anomalous grain growth and the formation of cord-like grains with an aspect ratio over 1000 and asymmetrical hillock/voids clusters were found. These abnormal morphological evolutions were resulted from the electron flow-induced lattice strains, which was inversely correlated with the lifespan of interconnection. Multi-phase alloys are less resistant to EM due to the unbalanced electron flow-induced strains.

The quantitative analysis of the crack propagation on the fatigue properties of dual-phase approximate equiaxial nanocrystalline AgCu alloy

Nanostructure dual-phase equiaxial alloy (DPEA) possesses the unique mechanical properties of high strength and ductility. However, the investigation of the fatigue properties in DPEA remains to be solved. In this paper, the mechanism of fatigue crack propagation in DPEA is explained by the interaction between dislocations and clusters in different grains of materials. The stress of dislocations on the slip plane and the time constant of pinned dislocation bypass the cluster can be calculated. The results show that the presence of clusters results in dislocations on the slip planes to induce different degrees of pile-up. The pile-up of dislocations is the dominant factor for hindering crack growth, which facilitates the crack blunting and improves the fracture toughness of alloy, during the plastic deformation of materials. In addition, based on the calculated results of the theoretical model, it is revealed that fracture toughness of DPEA is sensitive to the grain size, activation energy and the time constant of dislocation bypass the cluster. In a word, this research has provided a rational framework to amply explain the fatigue properties of DPEA based on theoretical model.

Wetting kinetics and interfacial structure of AgCu alloy spreading on TB8 substrates

AgCu filler metal spreading over TB8 substrate under a high-purity argon atmosphere was conducted at 920 °C. Effects of surface roughness and topography of the substrate on the wetting kinetics were investigated. The interfacial microstructures of AgCu eutectic alloy/TB8 substrate solidified couples was analyzed by optical microscope, scanning electron microscope, energy dispersive spectrometer and transmission electron microscope. Results revealed that the substrate surface roughness and topography had significant influences on the wetting kinetics and spreading process. The spreading was preferential when AgCu molten metal over an anisotropically microstructured surface. When the surface of the substrate was not anisotropic, the spreading morphology was almost a perfect circle. An additional capillary driving force exists when the molten metal flows on the rough surface, which leads to a better wettability. The interfacial microstructure of the resolidified AgCu on the TB8 substrate was Ag(ss)/ Ti3Cu4/Ti2Cu/ /Ti(ss) + Ti2Cu/TB8, and the spreading edge domain near the triple-line is rich in Ag.

Probing the effect of combustion controlled surface alloying in silver and copper towards ORR and OER in alkaline medium

Bi-metallic silver-copper nanoparticles were synthesized using two modes of combustion synthesis, known as Solution Combustion Synthesis (SCS) and Second Wave Combustion Synthesis (SWCS) to enhance surface alloying in Cu and Ag. The alloying in Ag and Cu nanoparticles was found to affect the adsorption of the oxygen molecule and synergistically increases the relative activity towards ORR and OER in 1M KOH medium. The catalyst sample AgCu-21, synthesized by the SWCS showed highest activity and stability due to high concentration of Ag-Cu alloy on surface as verified by XPS, TEM and phase mapping of elements on the surface. The ORR catalyzed by AgCu-21 proceed through an overall four-electron pathway with a kinetic current density of 12.4mAcm−2 at −0.2V potential. The XPS analysis of the samples indicates that the ORR and OER activity correlate well with the shifting in binding energy of Ag on Cu surface with higher degree of alloying resulting in better electrocatalytic performance.

Molecular dynamic study on the deformation mechanism based on strain rate, solute atomic concentration and temperature in dual-phase equiaxial nanocrystalline AgCu alloy

Nanocrystalline (NC) AgCu alloys have been attracted significant attention because of excellent electrical and mechanical properties. The microstructural evolution and deformation mechanisms are still challenging issues, and it is hard to observe directly by experimental methods. Accordingly, in this paper, atomic simulations are performed to investigate the tensile behavior of dual-phase equiaxial NC AgCu alloy (DPEA) at different strain rate (104-107 s−1), solute atomic concentration (5–20%) and temperature (300–600 K) using embedded atom method (EAM) potential. Relevant stress-strain curves and yield stress have been obtained. Result analysis reveals dislocation motion, atomic diffusion and grain boundary (GB) sliding are dominating deformation mechanisms. With the increase of strain rate and deformation, main deformation mechanisms are discovered to change from dislocation motion to GB sliding. Furthermore, the increase of solute atomic concentration (SAC) and temperature will promote the atomic diffusion and GB sliding. This work explains evolution process on deformation mechanisms of DPEA. It provides a qualitative analysis to design excellent mechanism property of DPEA by means of optimizing material structure parameters.

Effect of Mold Temperature on Surface Segregation of Continuous Unidirectional Solidified Cu-Ag Alloy

The Cu–3%Ag alloy was prepared by continuous unidirectional solidification technique. The composition distribution of continuous unidirectional solidification Cu–3%Ag alloy was analyzed. The effect of different mold temperatures on the composition distribution of alloy was studied. The results show that when the mold temperature is low, continuous unidirectional solidification Cu–3%Ag alloy has surface segregation. The morphology of segregation phase mainly presents stripe and water drop shape. When the mold temperature is high, the surface segregation begins to decrease and eventually disappear.

Pressureless Silver Sintering Property of SiC Device and ZTA AMB Substrate for Power Module

We have developed pressureless silver sintering module using zirconia toughened alumina (ZTA) substrate made of active metal brazing (AMB) and SiC device for power module. The silver paste was printed with a metal mask of 80, 120, and 150 μm thickness, respectively. The void content was measured by x-ray images after pressureless silver sintering under a vacuum and nitrogen atmosphere. In order to evaluate the durability against thermal stress of the sintered module, the thermal cycle test (TC) and the high temperature storage test (HTS) were conducted. The void content and bond strength before and after the environment test were measured. As a result, the void content did not change, but the bonding strength was decreased after TC and increased after HTS. Crack was generated at between silver sintered joint and ZTA substrate after TC test. Also, we observed that Cu-Ag alloy layer was formed between the copper AMB and silver sintered layer after HTS, which finally leaded to improve the bonding strength. Key words: Power module, Silver paste, Pressureless, Silver sintering, Bonding strength, Interface

A modified constitutive model and hot compression instability behavior of Cu-Ag alloy

Abstract The hot compressive deformation behaviors of Cu−6wt.%Ag alloy were studied experimentally in the temperature range of 973−1123 K and the strain rate range of 0.01−10 s−1. The stress increases and reaches the maximum value when the true strain is very small, and then the stress changes slowly and tends to be stable under the action of work hardening, dynamic recovery and recrystallization. The material parameters of the conventional Arrhenius constitutive model are only related to strain under different deformation conditions, and the prediction error is large, which cannot accurately characterize the hot deformation behavior of the alloy. To describe the hot deformation behavior of the alloy accurately, a modified constitutive model was established by considering the simultaneous influence of forming temperature, strain rate and strain. The results indicate that correlation coefficient (R) and the average absolute relative error (AARE) are 0.993 and 4.2%, respectively. The modified constitutive model can accurately describe the hot deformation behavior of Cu−6wt.%Ag alloy.

Facile synthesis and bi-functionality of mesoporous TiO2 implanted with AgCu alloy

Here, by a simple one-step in situ chemical reduction method, the AgxCuy alloy was tailored on the surface of mesoporous TiO2 (M-TiO2), therefore, a series of bi-functional mesoporous TiO2 nanohybrids (M-TiO2/AgxCuy) for both surface enhanced Raman scattering (SERS) detection and photocatalytic degradation of ampicillin (AMP) were achieved. The composition and structure of the nanohybrids were well characterized using XRD, TEM, XPS and HRTEM-EDS measurements. Results indicated that AgxCuy alloy was mainly attached around the pores of M-TiO2 which may generate more active sites than nonporous P25−Ag−Cu. Thus, the M-TiO2/AgxCuy nanohybrids could be used as efficient SERS substrates to sensitively monitor the AMP in water with lower detection limit (˜ 1 ppt) than P25−Ag−Cu. Besides, the M-TiO2/Ag3Cu1 nanohybrid also showed higher photocatalytic activities for the degradation of AMP under UV irradiation over the M-TiO2/Ag, the M-TiO2/Cu and the P25−Ag−Cu. This work provided a simple and effective approach to synthesize bi-functional nanohybrids for detection and degradation of organic contaminants in wastewater.

Facile synthesis of nearly monodisperse AgCu alloy nanoparticles with synergistic effect against oxidation and electromigration

Abstract

Synthesis and characterization of Ag-Cu alloy nanoparticles for antimicrobial applications: A polydopamine chemistry application

Synthesis and characterization of Ag-Cu alloy nanoparticles for antimicrobial applications: A polydopamine chemistry application