Cu-Zn Alloy Research Articles

Bulk Diffusion Regulated Nanopore Formation During Vapor Phase Dealloying of a Zn-Cu Alloy

Bulk Diffusion Regulated Nanopore Formation During Vapor Phase Dealloying of a Zn-Cu Alloy

Nanoporous Copper Ribbons Prepared by Chemical Dealloying of a Melt-Spun ZnCu Alloy

Nanoporous Copper Ribbons Prepared by Chemical Dealloying of a Melt-Spun ZnCu Alloy

Using ZnCu alloy as a facile and effective anti-scale strategy for cathode cleaning during electrocatalytic advanced oxidation processes (EAOPs) of oil-field wastewater

Electrocatalytic advanced oxidation processes (EAOPs) is a promising strategy for treating oil-bearing wastewater, However, scale growth on cathode is a severe problem impede its practical application in long-term process. In present paper, a ZnCu alloy was first used as an anti-scale filler for EAOPs, where Zn2+ can be released through electrolysis and can inhibit the scale formation on cathodes by disturbing the formation of CaCO3 scale. The scale phase can be transformed from stable calcite (hexahedron-shaped) into less stable aragonite (needle-like) and unstable vaterite (microspheroidal), which are easier to be removed by the shearing force of water. The influence of current density, temperature, pH and alloy dosage on scale inhibition were investigated in details. High current density leads to more H2 bubbles around cathode, which can contribute to a loosen scale and a protection layer around cathode which retards the moving of Ca2+ towards cathode. Temperature, on the other hand, could influence scale deposition by influencing the CaCO3 solubility in wastewater. Alkaline environment is adverse to scale inhibition because it leads to extra Zn2+ consumption in the form of Zn(OH)2. Our strategy provides a practical and new strategy for scale inhibition during EAOP.

Wear of cemented carbide forging dies used in zipper production

Cemented carbide tools are commonly used in both cutting and forging processes associated to zipper production. In production, the tools experience many millions of repeated contacts, hence they must be very durable to keep the wear at acceptable levels. Although the zipper elements in this investigation are made in a relatively soft CuZn alloy, the wear becomes significant and the tool life a production limiting factor. The wear process is to a large extent unknown. To increase the understanding, forging dies used for an increasing number of forgings in actual production, have been studied in detail. Initially the Co binder is preferentially worn off, and transferred CuZn partly fills the cavities. Interestingly, the repeating forging contacts lead to modification of the composition of the transferred material, which partly separates into Cu rich and Zn rich parts, where the Zn rich parts show a high presence of oxygen. During the life span of the tool, represented by the controlled use of forging tools to different percentages of their estimated life, the WC grains are gradually worn into faceted shapes. The most severely worn region of the forging dies develops an increasing surface roughness, which act to shape a corresponding pattern on the zipper elements.

Microstructure and crystallographic texture of Cu-Zn alloys subjected to ECAP and flat rolling

This paper presents the results of the microstructure and crystallographic texture investigations of the Cu-Zn alloys system with different stacking fault energies (SFE) subjected to severe plastic deformation (SPD) by equal channel angular pressing (ECAP) and subsequent flat rolling. It is shown that ECAP leads to the formation of an ultrafine-grained (UFG) structure. Further flat rolling is accompanied by a decrease in the size of structural elements and the formation of nanoscale twins, which are more likely to be detected in an alloy with a lower SFE. As the deformation degree increases, the main crystallographic textures components of the investigated alloys become Brass and Goss components.

Effect of SFE on the evolution of crystallographic texture in Cu-Zn alloys subjected to severe plastic deformation

Within the framework of experimental investigations and computer modeling using the viscoplastic self-consistent (VPSC) model of a material plastic flow, the regularities of preferential orientations formation were established, the proportion of certain texture components was estimated, and existing slip systems (SS) and twinning systems (TS) were identified for equal-channel angular pressing (ECAP) of copper alloys depending on the stacking fault energy (SFE).

Eco-Friendly Roselle (Hibiscus Sabdariffa) Leaf Extract as Naturally Corrosion Inhibitor for Cu-Zn Alloy in 1M HNO3

The eco-friendly compounds especially plant extracts have emerged as green corrosion inhibitors for metals and alloys. The inhibiting impact of Roselle extract on Cu-Zn alloy in 1M HNO3 solution was studied by weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP). It was found that Roselle extract acts as a good mixed-type corrosion inhibitor for Cu-Zn alloy in acid solution. The corrosion rate decreases with increasing the extract concentration and increases with raising the temperature. The formation of a protecting film on the Cu-Zn alloy surface with the presence of Roselle extract was confirmed by scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The high inhibition efficiency of 94.89 % was recorded for 80% extract solution. There are good agreements between the results from all techniques.

Developing α/β Laminar Composite Structure in CuZn Alloy by Heat Treatment and Submerged Friction Stir Processing

A laminar composite structure was developed in a CuZn alloy plate by non-equilibrium heat treatment and subsequent submerged friction stir processing. For this aim, Cu-37 wt.% Zn alloy was initially heat treated to produce a double phase structure. Then, the double phase plate was friction stir processed in underwater media at room temperature. The microstructure and mechanical properties of the samples were analyzed using optical microscopy and tensile test. During heat treatment, the large α grains containing annealing twins converted to a double phase structure with β grains on the α grain boundaries. Heat treatment caused an increase in ultimate tensile strength from 240 MPa to 275 MPa, and a reduction in elongation from 67 to 49%. After friction stir processing, the ultimate tensile strength and elongation were obtained as 380 MPa and 48%, respectively. This desirable mechanical property was achieved due to the formation of a novel composite structure containing parallel ultra-fine grained β layers between dynamically recrystallized α layers.

(Invited) All Electrochemical Synthesis of Nanoporous Cu Films for the Purposes of Fine Pitch and Low Temperature Interconnection in 3D Packaging

Nanoporous Cu (np-Cu) films can be employed in the electronic packaging as materials facilitating chip-to-substrate interconnections, which is realized by Cu-on-Cu bonding. Unlike their bulk counterparts, np metals feature unique interconnected pore-ligament structure with a length scale in the range of single-to-tens of nanometers. This results in a high surface area-to-volume ratio accompanied with a substantially lower melting temperature. Research has been done in the field to experiment with Cu-on-Cu interconnects realized by np-Cu precursor films (1). While the initial results are undoubtedly promising, difficulties haver been met with sufficiently lowering the sintering / soldering temperature below 380-400oC. A way to address these shortcomings is to develop of approaches to sintering at much lower temperatures by introducing Sn into the np-Cu structures either directly or by coating then followed by processing to produce at lower sintering temperature Cu-Sn bonds with low resistivity and a greater current carrying capability than bare np-Cu. The foundation of this study relies on the development of fine structured np-Cu films with an open and uniform interconnected network of ultra-fine ligaments and pores of size preferably in the single digit nanometer range.The present report is focused on the development of a two-step all-electrochemical approach for the synthesis of the targeted np-Cu structures including (i) a controlled electrodeposition of Cu-based precursor alloy with a less-noble counterpart that is then (ii) selectively removed (de-alloyed) by anodization at appropriate potential to leave behind the desired “spongy” np-Cu structure (2). Therefore, the first part of this report introduces and discusses the development of protocols for flat and uniform deposition of Cu-Zn and Cu-Mn alloys that could both serve as precursors of the synthetically targeted np-Cu films. The choice of said alloy systems is motivated by the ability of Zn and Mn to form single-phase alloys or intermetallic compounds with Cu thus ensuring the ultra-fine length scale of the eventually synthesized np Cu structure. The alloy deposition routines included use of a pyrophosphate (P2O7 4-) plating bath for Cu-Zn alloys which were shown to have high stability and optimizable for the plating of smooth and fine-grained brass deposits (3). Also, ammonium sulfate with excess of ammonia as complexing agent, was employed in the optimization activity aimed at the deposition of continuous and relatively smooth Cu-Mn deposits (4). The report discusses the optimization of plating parameters and conditions along with the subsequent structural and compositional characterization of the accordingly deposited precursor alloys with 60 at % and higher representation of the less noble constituent.Next, the electrochemical de-alloying of as-deposited CuxZn(1-x) and CuxMn(1-x) precursor alloys on a gold substrate is introduced and discussed. Alike with the first part of the report, the emphasis is on the optimization routines that looked at the effect of de-alloying scan rate, de-alloying at different constant potentials, de-alloying bath, and precursor alloy composition on the morphology and composition of the resulting np-Cu. A valuable part of the report is the demonstration of how the implementation of best combinations of optimized parameters and conditions leads to the synthesis of interconnected pore-ligament thin film networks of np-Cu structures with average ligament sizes in the range of 15-30 nm. In conclusion, the discussion takes direction towards ideas and perspectives for improvement of the uniformity and further refinement of the pore ligament length scale. Finally, consideration is also given to the intended approaches to introduce Sn on or into the accordingly synthesized np-Cu films and eventually convert them to np-Cu-Sn alloy ready for sintering/soldering at low temperatures.

Influence of Pulsed Current on Electrodeposited CuZn Alloys Structures and Thermal Stability

Brass is the leading copper alloys produced in the world as it offers excellent thermal and conductivity properties, directly linked to its zinc content. If cast-alloys are available in a broad range, it is only recently that electrodeposited CuZn by DC have been obtained with zinc mass content between 1 to 99% from a cyanide-free electrolytes [1], and their different microstructures characterized in range of 30 to 45% of zinc. Nevertheless, thick deposits are difficult to obtain with direct current, particularly while elaborating deposits with low zinc contents. This is related to the low current densities requested to get the lowest zinc content deposits, which constitutes a limitation of the process.Surprisingly, when using pulsed current with small Duty Cycle values with average currents comparable or greater to DC ones, the zinc content is kept at low %, even if the peak currents densities are higher (to compensate the toff times) normally inducing the opposite effect. This can be explained by the electroless deposition of copper, which occurs during the toff times because of the specification of the electrolyte. Therefore, with the adequate pulse current parameters, it is possible to obtain CuZn deposits with higher deposition rates, and finally deposits with thicknesses up to 8 µm after one hour, in the zinc content range of 35-45%. For all the samples, an improvement in both homogeneity and brightness was also noticed while compared to those elaborated by DC.Therefore, Rietveld refinement was applied on the XRD diffractograms of electrodeposits brass to study the effect of thermal treatment on the structure stability particularly on phases distribution, and both of crystals size and orientations. Potentiodynamic oxidation curves were used to determine CuZn electrodeposited crystalline structures, by optimizing the evaluation of the relative participation of each phase present in the dissolved deposit in the global response with a deconvolution using the Gaussian normal distribution.

In situatomic-scale observation of the conversion behavior in a Cu-Zn alloy for twinnability enhancement

Cu-Zn based alloys have been widely used in various applications due to their outstanding properties, such as high electrical conductivity and increased hardness over pure Cu. The thermal effect during electrical conduction leads to the requirement of excellent thermal stability for maintaining performance, which is strongly related to the microstructural transformation and kinetics. However, the atomic-scale microstructural evolution of Cu-Zn systems has scarcely been discussed. In this study, the reaction process of Cu-Zn systems was observed via in situ high-resolution transmission electron microscopy (in situ HRTEM). The Zn/Cu thin films were converted to β-CuZn at 180 ℃ and exhibited an epitaxial relationship with Cu, which was described as (01 1¯)β-CuZn // (1¯11)Cu and [100]β-CuZn // [110]Cu. Subsequently, the Cu-rich solid solution (α phase) was formed at 300 ℃ to decrease the Gibbs free energy, where layer-by-layer diffusion took place on the (1¯1¯ 1) plane. Based on the improved twinnability of the α phase with decreasing stacking fault energy (SFE), nanotwins grew along with the α phase. The twin boundaries effectively retard atomic migration, which is expected to optimize the mechanical properties. The fundamental science described in this study provides novel insights into Cu-Zn alloys, which could be explored in a wide range of alloy systems.

Impact of sterilization treatments on biodegradability and cytocompatibility of zinc-based implant materials

Biodegradable zinc (Zn) and Zn-based alloys have been recognized as promising biomaterials for biomedical implants. Sterilization is an essential step in handling Zn-based implants before their use in clinical practice and there are various sterilization methods are available. However, how these treatments influence the Zn-based biomaterials remains unknown and is of critical relevance. In this study, three commonly-applied standard sterilization methods, namely gamma irradiation, hydrogen peroxide gas plasma and steam autoclave, were used on pure Zn and Zn3Cu (wt%) alloy. The treated Zn and ZnCu alloy were investigated to compare the different influences of sterilizations on surface characteristics, transient and long-term degradation behavior and cytotoxicity of Zn and Zn alloy. Our results indicate that autoclaving brought about apparently a formation of inhomogeneous zinc oxide film whereas the other two methods produced no apparent alterations on the material surfaces. Consequently, the samples after autoclaving showed significantly faster degradation rates and more severe localized corrosion, especially for the ZnCu alloy, owing to the incomplete covering and unstable zinc oxide layer. Moreover, the autoclave-treated Zn and ZnCu alloy exhibited apparent cytotoxic effects towards fibroblasts, which may be due to the excessive Zn ion releasing and its local concentration exceeds the cellular tolerance capacity. In contrast, gamma irradiation and hydrogen peroxide gas plasma had no apparent adverse effects on the biodegradability and cytocompatibility of Zn and ZnCu alloy. Our findings may have significant implications regarding the selection of suitable sterilization methods for Zn-based implant materials among others.

Investigation on microstructures, mechanical properties and in vitro corrosion behavior of novel biodegradable Zn-2Cu-0.01Ti-xLi alloys

The poor mechanical properties of pure Zn almost exclude the possibility of using it as biodegradable implant material. Therefore, alloy design and process strategy of biodegradable Zn alloys have been the focus of attention. In this work, novel biodegradable Zn-2Cu-0.01Ti-xLi (x = 0, 0.1 and 0.38) alloys were designed and fabricated (cast, annealed and extruded) to investigate their microstructures, mechanical properties and corrosion behavior. The results showed that primary ɛ-CuZn4 particles and eutectic TiZn16 phase are formed in all the as-cast alloys. However, the size and volume fraction of the primary particles in the Zn-2Cu-0.01Ti-0.38Li alloy are significantly increased. Also, wavy lamellar β-LiZn4 phase precipitates from the Zn matrix of this alloy. In the as-annealed microstructures, secondary lath-like ɛ-CuZn4 phase is formed around the primary ɛ-CuZn4 particles in the Zn-2Cu-0.01Ti and Zn-2Cu-0.01Ti-0.1Li alloys. The above phases are broken, crushed or elongated in the as-extruded alloys, playing a crucial role in enhancing their strength. All the as-cast alloys show inferior mechanical properties, especially poor ductility. By contrast, the as-extruded alloys exhibit significantly improved mechanical properties. The as-extruded Zn-2Cu-0.01Ti alloy has elongation of up to 130 ± 5.60%, exhibiting ultrahigh tensile ductility. The as-extruded Zn-2Cu-0.01Ti-0.38Li alloy possesses tensile yield strength, ultimate tensile strength, tensile elongation, compression yield strength, and ultimate compression strength of 408 ± 16.6 MPa, 431 ± 7.9 MPa, 68 ± 4.05%, 393 ± 13.2 MPa and 1030 ± 25.2 MPa, respectively, showing the best comprehensive mechanical properties. Both electrochemical and in vitro immersion corrosion tests show that the Zn-2Cu-0.01Ti and Zn-2Cu-0.01Ti-0.38Li alloys have the highest and lowest corrosion rates, respectively. Adding Ti and Li to Zn-Cu alloy can reduce and improve its corrosion resistance, respectively.

Triggering Water and Methanol Activation for Solar-Driven H2 Production: Interplay of Dual Active Sites over Plasmonic ZnCu Alloy.

Methanol steam reforming (MSR) is a promising reaction that enables efficient production and safe transportation of hydrogen, but it requires a relatively high temperature to achieve high activity, leading to large energy consumption. Here, we report a plasmonic ZnCu alloy catalyst, consisting of plasmonic Cu nanoparticles with surface-deposited Zn atoms, for efficient solar-driven MSR without additional thermal energy input. Experimental results and theoretical calculations suggest that Zn atoms act not only as the catalytic sites for water reduction with lower activation energy but also as the charge transfer channel, pumping hot electrons into water molecules and subsequently resulting in the formation of electron-deficient Cu for methanol activation. These merits together with photothermal heating render the optimal ZnCu catalyst a high H2 production rate of 328 mmol gcatalyst-1 h-1 with a solar energy conversion efficiency of 1.2% under 7.9 Suns irradiation, far exceeding the reported conventional photocatalytic and thermocatalytic MSR. This work provides a potential strategy for efficient solar-driven H2 production and various other energy-demanding industrial reactions through designing alloy catalysts.

Revamping SiO2 Spheres by Core–Shell Porosity Endowment to Construct a Mazelike Nanoreactor for Enhanced Catalysis in CO2 Hydrogenation to Methanol

AbstractBeyond the catalytic activity of nanocatalysts, the support with architectural design and explicit boundary could also promote the overall performance through improving the diffusion process, highlighting additional support for the morphology‐dependent activity. To delineate this, herein, a novel mazelike‐reactor framework, namely multi‐voids mesoporous silica sphere (MVmSiO2), is carved through a top‐down approach by endowing core‐shell porosity premade Stöber SiO2 spheres. The precisely‐engineered MVmSiO2 with peripheral one‐dimensional pores in the shell and interconnecting compartmented voids in the core region is simulated to prove combined hierarchical and structural superiority over its analogous counterparts. Supported with CuZn‐based alloys, mazelike MVmSiO2 nanoreactor experimentally demonstrated its expected workability in model gas‐phase CO2 hydrogenation reaction where enhanced CO2 activity, good methanol yield, and more importantly, a prolonged stable performance are realized. While tuning the nanoreactor composition besides morphology optimization could further increase the catalytic performance, it is accentuated that the morphological architecture of support further boosts the reaction performance apart from comprehensive compositional optimization. In addition to the found morphological restraints and size‐confinement effects imposed by MVmSiO2, active sites of catalysts are also investigated by exploring the size difference of the confined CuZn alloy nanoparticles in CO2 hydrogenation employing both in‐situ experimental characterizations and density functional theory calculations.

Nucleation and growth mechanism of Cu-Zn/AgNPs composite coatings at different concentrations of silver nanoparticles (AgNPs) in solution

Atomic force microscopy (AFM), X-ray Diffraction (XRD), and electrochemical techniques (voltammetry and chronoamperometry) were used to evaluate the influence of the concentration of silver nanoparticles (AgNPs) on the electrodeposition and nucleation mode of Cu-Zn/AgNPs composite coatings. The voltammetry analysis display three reduction processes during the formation of the Cu-Zn/AgNPs metal composite. The first process (peakPCI) appears in the potential range of -0.5 to -1.2 V vs. saturated calomel electrode (SCE) and corresponds to the reduction of Cu(II) to Cu(0). The second and the third processes, peak PCII and PCIII, respectively are located in the range of -1.4 to -1.6 V vs. SCE and are associated with the deposition of various crystalline phases of the Cu-Zn alloy. The potential of the PCI peak is shifted in the negative direction by increasing the concentration of AgNPs in the electrolytic solution. This effect is related to the adsorption of AgNPs on the substrate surface. From the chronoamperometry study, it was possible to disclose a process of nucleation and growth of phases in the potential region where the peak PCI is formed. This nucleation process may be explained in terms of a combination of an adsorption process and a diffusion-controlled three-dimensional crystal nucleation and growth mechanism (3D−dc(PcI)). In the potential range where the PCII and PCIII peaks appear, a second nucleation process take place. This nucleation process involves three mechanisms: an adsorption process and two three-dimensional (3D) mechanisms of the kinetics of nucleation and diffusion-controlled growth of bimetallic phases (3Ddc−bimetal) that correspond to the nucleation of various phases of the alloys. On the other hand, a decrease in the nucleation kinetics parameters (density of active sites formed (N0) and the nucleation rate (A)) is observed with the increasing concentration of the AgNPs in the electrolytic solution. XRD analysis confirmed the formation of various crystalline structures of the Cu-Zn alloy at -1.50 V vs. SCE. Furthermore, AFM showed that the morphology and size of the formed metal clusters strongly depend on the content of the AgNPs in the bath.

Dynamic Recrystallization and Its Effect on Superior Plasticity of Cold-Rolled Bioabsorbable Zinc-Copper Alloys.

High plasticity of bioabsorbable stents, either cardiac or ureteral, is of great importance in terms of implants’ fabrication and positioning. Zn-Cu constitutes a promising group of materials in terms of feasible deformation since the superplastic effect has been observed in them, yet its origin remains poorly understood. Therefore, it is crucial to inspect the microstructural evolution of processed material to gain an insight into the mechanisms leading to such an extraordinary property. Within the present study, cold-rolled Zn-Cu alloys, i.e., Zn with addition of 1 wt.% and 5 wt.% of Cu, have been extensively investigated using scanning electron microscopy as well as transmission electron microscopy, so as to find out the possible explanation of superior plasticity of the Zn-Cu alloys. It has been stated that the continuous dynamic recrystallization has a tremendous impact on superior plasticity reported for Zn-1Cu alloy processed by rolling to 90% of reduction rate. The effect might be supported by static recrystallization, provoking grain growth and thereby yielding non-homogeneous microstructures. Such heterogeneous microstructure enables better formability since it increases the mean free path for dislocation movement.

Research on the Microstructure and Mechanical Properties of WC-TiC-Co/steel Joints

Wear-resistant layer of cemented carbide on steel can improve its wear properties in particular areas, such as oil drilling. Herein, the WC-TiC-Co/steel joint, the WC-TiC-Co wear-resistant layer covers the steel surface, is fabricated by infiltration brazed, using Cu-Zn filler alloy and WC particles as solder. The microstructure and mechanical properties of as-obtained joint are investigated. The Longitudinal interface has good bonding and the existence of transverse gaps are surveyed on interface between WC-TiC-Co and solder. The element Mapping test shows the distribution of Co element in WC-TiC-Co block is uneven. And the present of element interdiffusion forms the diffusion layer in the joining zone between base materials and solder. The hardness and phase tests indicate that Co3Fe7, W2C phase were produced during brazing, but there are few impacted on the hardness by Co3Fe7, W2C phase.

Zn-Mg and Zn-Cu alloys for stenting applications: From nanoscale mechanical characterization to in vitro degradation and biocompatibility

In the recent decades, zinc (Zn) and its alloys have been drawing attention as promising candidates for bioresorbable cardiovascular stents due to its degradation rate more suitable than magnesium (Mg) and iron (Fe) alloys. However, its mechanical properties need to be improved in order to meet the criteria for vascular stents. This work investigates the mechanical properties, biodegradability and biocompatibility of Zn-Mg and Zn-Cu alloys in order to determine a proper alloy composition for optimal stent performance. Nanoindentation measurements are performed to characterize the mechanical properties at the nanoscale as a function of the Zn microstructure variations induced by alloying. The biodegradation mechanisms are discussed and correlated to microstructure, mechanical performance and bacterial/cell response. Addition of Mg or Cu alloying elements refined the microstructure of Zn and enhanced yield strength (YS) and ultimate tensile strength (UTS) proportional to the volume fraction of secondary phases. Zn-1Mg showed the higher YS and UTS and better performance in terms of degradation stability in Hanks’ solution. Zn-Cu alloys presented an antibacterial effect for S. aureus controlled by diffusion mechanisms and by contact. Biocompatibility was dependent on the degradation rate and the nature of the corrosion products.

First principles inelastic mean free paths coupled with Monte Carlo simulation of secondary electron yield of Cu-Ni, Cu-Zn, and Mo-Li

Secondary electron yield (SEY) is relevant for widely used characterization methods (e.g., secondary electron spectroscopy and electron microscopy) and materials applications (e.g., multipactor effect). Key quantities necessary for understanding the physics of electron transport in materials and simulation of SEY are electron mean free paths (MFPs). This paper explores the impact of alloying on MFPs and SEY for Cu-Ni, Cu-Zn, and Mo-Li alloys relative to their component metals Cu, Ni, Zn, Mo, and Li. Density functional theory calculations yield density of states, Fermi energy, work function, and frequency- and momentum-dependent energy loss function. These material properties were used to calculate MFPs and Monte Carlo simulations were performed to obtain energy dependent SEY for the alloys as well for the component metals. The results show that MFPs and SEYs of the studied alloys lie between those of component pure elements but are not a simple composition weighted average. Detailed analysis of the secondary electron generation and emission process shows that the changes in the SEY of alloys relative to the SEY of their component metals depend on the changes in both electronic structure and dielectric properties of the material.