Pure Zn Research Articles

Comparative Study of Electrodeposited Zn and Zn–Ni Alloy Coatings for Improved Corrosion Protection in Chloride Medium

The anti-corrosive Zn and Zn–Ni alloy coatings were electrodeposited on different copper substrates using an optimized sulphate electrolyte bath by conventional Hull cell method with glycine as an additive. The composition and surface morphology of the coatings were dependent on the current density. The co-deposition of Zn and Ni in Zn–Ni alloy showed anomalous behaviour, wherein, the deposition of less noble metal (Zn) was preferred over the more noble (Ni) metal. Anticorrosion properties of the coatings were experimented by electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques in 3.5% NaCl medium. The Zn–Ni alloy exhibited 3 times better corrosion resistance than pure Zn coating under the same deposition conditions.

Study on Anti-Aging Zn-Mg-WC Nanocomposites for Bioresorbable Cardiovascular Stents: Microstructure, Mechanical Properties, Fatigue, and <i>in vitro</i> Corrosion

Zinc (Zn) and Zn-based alloys have been extensively studied as innovative materials for bioresorbable stents (BRS) in the last decade due to their favorable biodegradability and biocompatibility. However, most Zn alloys lack the necessary combination of adequate strength, ductility and corrosion rate needed for such clinical applications. Additionally, due to the low melting temperature of Zn, Zn-based alloys are also thermally unstable and undergo microstructural changes over time at ambient and physiological temperatures, which negatively impacts the mechanical properties during storage, implantation, and service. In this study, tungsten carbide (WC) nanoparticles were successfully incorporated into Zn alloyed with 0.5 wt.% magnesium (Mg). The resulting Zn-0.5Mg-WC nanocomposite’s microstructure, mechanical properties, in vitro corrosion rate and aging behavior were evaluated. SEM and TEM microstructural analysis showed that Mg2Zn11 precipitates with a granular morphology formed at the Zn/WC nanoparticle interface. This microstructure resulted in a combination of enhanced strength and ductility, and the Zn-0.5Mg-WC nanocomposite was able to survive at least 10 million cycles of tensile loading. Due to the granular precipitate morphology, the loss of ductility caused by aging was not observed over a 90-day study. Furthermore, the Zn-0.5Mg-WC nanocomposite had an in vitro corrosion rate comparable to pure Zn, which is ideal for BRS applications. Stent prototypes were fabricated using this composition and were successfully deployed during bench testing without fracture. This study shows that the Zn-0.5Mg-WC nanocomposite is a promising material for BRS applications.

Hierarchical microstructure and two-stage corrosion behavior of a high-performance near-eutectic Zn-Li alloy

In order to improve mechanical and corrosion properties of biodegradable pure Zn, a knowledge-based microstructure design is performed on Zn-Li alloy system composed of hard β-LiZn4 and soft Zn phases. Precipitation and multi-modal grain structure are designed to toughen β-LiZn4 while strengthen Zn, resulting in high strength and high ductility for both the phases. Needle-like secondary Zn precipitates form in β-LiZn4, while fine-scale networks of string-like β-LiZn4 precipitates form in Zn with a tri-modal grain structure. As a result, near-eutectic Zn-0.48Li alloy with an outstanding combination of high strength and high ductility has been fabricated through hot-warm rolling, a novel fabrication process to realize the microstructure design. The as-rolled alloy has yield strength (YS) of 246 MPa, the ultimate tensile strength (UTS) of 395 MPa and elongation to failure (EL) of 47 %. Immersion test in simulated body fluid (SBF) for 30 days reveals that Li-rich products form preferentially at initial stage, followed by Zn-rich products with prolonged time. Aqueous insoluble Li2CO3 forms a protective passivation film on the alloy surface, which suppresses the average corrosion rate from 81.2 μm/year at day one down dramatically to 18.2 μm/year at day five. Afterwards, the average corrosion rate increases slightly with decrease of Li2CO3 content, which undulates around the clinical requirements on corrosion resistance (i.e., 20 μm/year) claimed for biodegradable metal stents.

Zinc alloys as prospective materials for biodegradable medical devices

Zinc-based materials are considered as promising materials for an application like biodegradable medical devices (bone fixations, stents). Such materials have to be characterized by an excellent combination of me-chanical, corrosion and biological properties. Presented paper is focused on the characterization of micro-structure and closely related mechanical properties for 3 zinc materials, namely pure Zn, Zn-0.8Mg and Zn-0.8Mg-0.2Sr. Studied alloys were prepared by gravity casting, homogenization treatment at 350 °C and extru-sion at 200 °C and extrusion ratio 11. Alloying by Mg caused the refinement of microstructure, formation of Mg2Zn11 phase and related improvement of mechanical properties like TYS and UTS for an extruded alloy. An additional encore of Sr causes a systematical improvement of TYS and UTS values, although the elonga-tion vas slightly decreased due to the presence of brittle SrZn13 phase.

Direct Self‐Assembly of MXene on Zn Anodes for Dendrite‐Free Aqueous Zinc‐Ion Batteries

Metallic zinc is a promising anode candidate of aqueous zinc-ion batteries owing to its high theoretical capacity and low redox potential. However, Zn anodes usually suffer from dendrite and side reactions, which will degrade their cycle stability and reversibility. Herein, we developed an in situ spontaneously reducing/assembling strategy to assemble a ultrathin and uniform MXene layer on the surface of Zn anodes. The MXene layer endows the Zn anode with a lower Zn nucleation energy barrier and a more uniformly distributed electric field through the favorable charge redistribution effect in comparison with pure Zn. Therefore, MXene-integrated Zn anode exhibits obviously low voltage hysteresis and excellent cycling stability with dendrite-free behaviors, ensuring the high capacity retention and low polarization potential in zinc-ion batteries.

Direct Self‐Assembly of MXene on Zn Anodes for Dendrite‐Free Aqueous Zinc‐Ion Batteries

AbstractMetallic zinc is a promising anode candidate of aqueous zinc‐ion batteries owing to its high theoretical capacity and low redox potential. However, Zn anodes usually suffer from dendrite and side reactions, which will degrade their cycle stability and reversibility. Herein, we developed an in situ spontaneously reducing/assembling strategy to assemble a ultrathin and uniform MXene layer on the surface of Zn anodes. The MXene layer endows the Zn anode with a lower Zn nucleation energy barrier and a more uniformly distributed electric field through the favorable charge redistribution effect in comparison with pure Zn. Therefore, MXene‐integrated Zn anode exhibits obviously low voltage hysteresis and excellent cycling stability with dendrite‐free behaviors, ensuring the high capacity retention and low polarization potential in zinc‐ion batteries.

FABRICATION AND CHARACTERISATION OF MG-ZN ALLOYS REINFORCED WITH CNF: A STUDY ON THE SINTERING PROCESS

Nowadays, magnesium (Mg) based alloys have gained much interest due to its potential use as biodegradable implants for the application of fixation, screws and plates in orthopaedics field. The main problems of biodegradable implants made from pure Mg are its low strength and easily corrodible. Therefore, the purpose of this study was to analyse the sintering temperature of magnesium-zinc (Mg-Zn) alloys reinforced with carbon nanofibres (CNF) through mechanical and morphological structures. Pure Mg, Zn, and CNF was prepared via powder metallurgy (PM) method. The samples were mechanically alloyed using planetary ball mill to create finer powder. Next, the samples were compacted using the Instron machine for 10 minutes at room temperature to produce a 10 mm diameter cylindrical platelet. Then, the specimens were heated with an argon gas flow for 4 hours at different sintering temperatures. The results showed that the optimum sintering temperature for Mg-Zn alloys reinforced with CNF was at 250℃ with elastic modulus and yield strength of 2729.886 MPa and 140.628 MPa, respectively. The findings of this study concluded that Mg-Zn alloys reinforced with CNF composites have great potential to be used as new biodegradable implants for medical applications in the future.

Friction spot extrusion welding-brazing of copper to aluminum alloy

Friction spot extrusion welding-brazing of pure copper to 5083 aluminum alloy sheet using pure Zn as interlayer has been elucidated. The effect of shoulder geometry on the microstructural characterizations and mechanical behavior of the joints was explored. Results indicated that changing the geometry of the shoulder from cylindrical to triangular not only enlarged the brazed zone from 14.98 μm to 19.65 μm, but also the tensile/shear strength had a rising trend and improved from 3268 N to 4398 N, which can be attributed to the larger brazed zone and complete filling of the pre-threaded hole in the joint produced by the triangular shoulder.

Biodegradable metals for bone fracture repair in animal models: a systematic review.

Biodegradable metals hold promises for bone fracture repair. Their clinical translation requires pre-clinical evaluations including animal studies, which demonstrate the safety and performance of such materials prior to clinical trials. This evidence-based study investigates and analyzes the performance of bone fractures repair as well as degradation properties of biodegradable metals in animal models. Data were carefully collected after identification of population, interventions, comparisons, outcomes and study design, as well as inclusion criteria combining biodegradable metals and animal study. Twelve publications on pure Mg, Mg alloys and Zn alloys were finally included and reviewed after extraction from a collected database of 2122 publications. Compared to controls of traditional non-degradable metals or resorbable polymers, biodegradable metals showed mixed or contradictory outcomes of fracture repair and degradation in animal models. Although quantitative meta-analysis cannot be conducted because of the data heterogeneity, this systematic review revealed that the quality of evidence for biodegradable metals to repair bone fractures in animal models is ‘very low’. Recommendations to standardize the animal studies of biodegradable metals were proposed. Evidence-based biomaterials research could help to both identify reliable scientific evidence and ensure future clinical translation of biodegradable metals for bone fracture repair.

The Effect of Ca on In Vitro Behavior of Biodegradable Zn-Fe Alloy in Simulated Physiological Environments

The growing interest in Zn based alloys as structural materials for biodegradable implants is mainly attributed to the excellent biocompatibility of Zn and its important role in many physiological reactions. In addition, Zn based implants do not tend to produce hydrogen gas in in vivo conditions and hence do not promote the danger of gas embolism. However, Zn based implants can provoke encapsulation processes that, practically, may isolate the implant from its surrounding media, which limits its capability of performing as an acceptable biodegradable material. To overcome this problem, previous research carried out by the authors has paved the way for the development of Zn-Fe based alloys that have a relatively increased corrosion rate compared to pure Zn. The present study aims to evaluate the effect of 0.3–1.6% Ca on the in vitro behavior of Zn-Fe alloys and thus to further address the encapsulation problem. The in vitro assessment included immersion tests and electrochemical analysis in terms of open circuit potential, potentiodynamic polarization, and impedance spectroscopy in phosphate buffered saline (PBS) solution at 37 °C. The mechanical properties of the examined alloys were evaluated by tension and hardness tests while cytotoxicity properties were examined using indirect cell metabolic activity analysis. The obtained results indicated that Ca additions increased the corrosion rate of Zn-Fe alloys and in parallel increased their strength and hardness. This was mainly attributed to the formation of a Ca-rich phase in the form CaZn13. Cytotoxicity assessment showed that the cells’ metabolic activity on the tested alloys was adequate at over 90%, which was comparable to the cells’ metabolic activity on an inert reference alloy Ti-6Al-4V.

The Renaissance of Liquid Metal Batteries

Next-generation batteries with long life, high-energy capacity, and high round-trip energy efficiency are essential for future smart grid operation. Recently, Cui et al. demonstrated a battery design meeting all these requirements—a solid electrolyte-based liquid lithium-brass/zinc chloride (SELL-brass/ZnCl2) battery. Such a battery design overcomes some inherent problems of conventional ZEBRA batteries and lithium ion batteries.

Microstructure and Electrochemical Performance Evaluation of Zn, Zn-5 wt.% Al and Zn-20 wt.% Al Alloy Coated Steels

A comparative study has been done on three coatings obtained on steel surface using pure Zn, two Zn-Al alloy baths. The coatings obtained using both Zn alloy baths are thinner than the same obtained using pure zinc bath as Al reacts with steel and forms very thin layer of Fe2Al5 phase which hinders iron-zinc reaction. Coating obtained using pure zinc bath predominantly consists of eta (~ 100 wt.% Zn) and zeta (FeZn13) phases in combination with less extent of delta (FeZn10) and gamma (Fe3Zn10) phases, whereas coatings obtained using Zn-Al alloy baths exhibit zinc-rich phase covered by aluminum rich phase with Al2O3 at the top. Al-rich phase content is higher for Zn-20 wt.% Al alloy coating. The coatings obtained on steel surfaces using both the Zn alloy baths show better ductility compared to pure zinc bath. This can be attributed to the presence of brittle Zn-Fe alloy phase in the coating obtained using pure zinc bath. The coatings obtained using both the Zn alloy baths were found to have a greater passivation characteristics compared to the coating obtained using pure zinc bath without compromising sacrificial characteristic of the coating. Electrochemical and salt spray tests results showed 3 and 6 times improved corrosion resistance properties of Zn-5 wt.% Al and Zn-20 wt.% Al alloy coatings than the pure zinc coating.

Biodegradable Zn–Sr alloy for bone regeneration in rat femoral condyle defect model: In vitro and in vivo studies

Bone defects are commonly caused by severe trauma, malignant tumors, or congenital diseases and remain among the toughest clinical problems faced by orthopedic surgeons, especially when of critical size. Biodegradable zinc-based metals have recently gained popularity for their desirable biocompatibility, suitable degradation rate, and favorable osteogenesis-promoting properties. The biphasic activity of Sr promotes osteogenesis and inhibits osteoclastogenesis, which imparts Zn–Sr alloys with the ideal theoretical osteogenic properties. Herein, a biodegradable Zn–Sr binary alloy system was fabricated. The cytocompatibility and osteogenesis of the Zn–Sr alloys were significantly better than those of pure Zn in MC3T3-E1 cells. RNA-sequencing illustrated that the Zn-0.8Sr alloy promoted osteogenesis by activating the wnt/β-catenin, PI3K/Akt, and MAPK/Erk signaling pathways. Furthermore, rat femoral condyle defects were repaired using Zn-0.8Sr alloy scaffolds, with pure Ti as a control. The scaffold-bone integration and bone ingrowth confirmed the favorable in vivo repair properties of the Zn–Sr alloy, which was verified to offer satisfactory biosafety based on the hematoxylin-eosin (H&E) staining and ion concentration testing of important organs. The Zn-0.8Sr alloy was identified as an ideal bone repair material candidate, especially for application in critical-sized defects on load-bearing sites due to its favorable biocompatibility and osteogenic properties in vitro and in vivo.

Investigating the stress corrosion cracking of a biodegradable Zn-0.8 wt%Li alloy in simulated body fluid

Stress corrosion cracking (SCC) may lead to brittle, unexpected failure of medical devices. However, available researches are limited to Mg-based biodegradable metals (BM) and pure Zn. The stress corrosion behaviors of newly-developed Zn alloys remain unclear. In the present work, we conducted slow strain rate testing (SSRT) and constant-load immersion test on a promising Zn-0.8 wt%Li alloy in order to investigate its SCC susceptibility and examine its feasibility as BM with pure Zn as control group. We observed that Zn-0.8 wt%Li alloy exhibited low SCC susceptibility. This was attributed to variations in microstructure and deformation mechanism after alloying with Li. In addition, both pure Zn and Zn-0.8 wt%Li alloy did not fracture over a period of 28 days during constant-load immersion test. The magnitude of applied stress was close to physiological condition and thus, we proved the feasibility of both materials as BM.

The influence of Ca and Cu additions on the microstructure, mechanical and degradation properties of Zn–Ca–Cu alloys for absorbable wound closure device applications

Novel ternary Zn–Ca–Cu alloys were studied for the development of absorbable wound closure device material due to Ca and Cu's therapeutic values to wound healing. The influence of Ca and Cu on the microstructure, mechanical and degradation properties of Zn were investigated in the as-cast state to establish the fundamental understanding on the Zn–Ca–Cu alloy system. The microstructure of Zn-0.5Ca-0.5Cu, Zn-1.0Ca-0.5Cu, and Zn0.5Ca-1.0Cu is composed of intermetallic phase CaZn13 distributed within the Zn–Cu solid solution. The presence of CaZn13 phase and Cu as solute within the Zn matrix, on the one hand, exhibited a synergistic effect on the grain refinement of Zn, reducing the grain size of pure Zn by 96%; on the other hand, improved the mechanical properties of the ternary alloys through solid solution strengthening, second phase strengthening, and grain refinement. The degradation properties of Zn–Ca–Cu alloys are primarily influenced by the micro-galvanic corrosion between Zn–Cu matrix and CaZn13 phase, where the 0.5% and 1.0% Ca addition increased the corrosion rate of Zn from 11.5 μm/y to 19.8 μm/y and 29.6 μm/y during 4 weeks immersion test.

Preparation of novel Zn/Gr MMC using a modified electro-co-deposition method: Microstructural and tribo-mechanical properties

Zinc is a well-suited low-cost and widely alloyed metal used in several metal matrix composites (MMCs) due to its easy availability, low melting point, excellent thermal and electrical properties. However, Zn metal alone is a low strength material which restricts its applications mostly for alloying purpose. Inclusion of graphene nano-reinforcements in Zn metal matrix could result in high strength and cost-effective nanocomposite material. In this paper, impermeable graphene nano-reinforcements are encapsulated in Zn metal matrix using a modified electro-co-deposition method followed by powder metallurgy. The uniform distribution of nano-reinforcement of graphene layers across the Zn metal matrix was achieved. The prepared nanocomposite was characterized and tested to evaluate the microstructural, morphological and tribo-mechanical properties. The graphene content in Zn matrix decreased the crystallite size and imparted the advantageous grain strengthening effect. The graphene reinforced Zn MMC sample showed a significant enhancement in the mechanical and tribological properties than that of pure Zn sample.

Fuzzy multicriteria decision-making-based optimal Zn–Al alloy selection in corrosive environment

Abstract Suitable material selection with emphasis on a specific property or application is an indispensable part of engineering sciences. It is a complex process that involves multiple criteria and often multiple decision makers. The tendency of decision makers to specify their preference in terms of imprecise qualitative statements like ‘good’, ‘bad’ etc. poses a further challenge. Thus, in this research, a comprehensive multicriteria decision-making study was conducted to select the optimal Zn-Al alloy based on performance in a corrosive environment. Four variants of technique for order of preference by similarity to the ideal solution were used to perform the multicriteria decision-making analysis. Group decision and imprecise decision making is handled by incorporating the fuzzy theory concept in a technique for order of preference by similarity to the ideal solution. The effect of addition of aluminium to zinc was studied by examination of microstructure, hardness, and corrosion behaviour. The result indicates that an increase in Al content increases the formation of dendrites. The dendrites were rich in the α phase, which results in an increase in hardness. An increase in Al content in Zn (Zn-22Al and Zn-55Al) results in the uniform distribution of the a phase in the microstructure and reduction of non-equilibrium phases. The potentiodynamic polarisation test revealed that an increase in Al in the alloy decreases the corrosion current density. The weight loss test carried out to validate the potentiodynamic test findings exhibited higher weight loss in pure Zn and lowest in Zn-55Al. Similar results were observed in the salt spray test. The multicriteria decision-making analysis revealed that Zn-55Al is the most suitable alloy in a corrosive environment among the tested alloys.

Fuzzy multicriteria decision-making-based optimal Zn–Al alloy selection in corrosive environment

Abstract Suitable material selection with emphasis on a specific property or application is an indispensable part of engineering sciences. It is a complex process that involves multiple criteria and often multiple decision makers. The tendency of decision makers to specify their preference in terms of imprecise qualitative statements like ‘good’, ‘bad’ etc. poses a further challenge. Thus, in this research, a comprehensive multicriteria decision-making study was conducted to select the optimal Zn-Al alloy based on performance in a corrosive environment. Four variants of technique for order of preference by similarity to the ideal solution were used to perform the multicriteria decision-making analysis. Group decision and imprecise decision making is handled by incorporating the fuzzy theory concept in a technique for order of preference by similarity to the ideal solution. The effect of addition of aluminium to zinc was studied by examination of microstructure, hardness, and corrosion behaviour. The result indicates that an increase in Al content increases the formation of dendrites. The dendrites were rich in the α phase, which results in an increase in hardness. An increase in Al content in Zn (Zn-22Al and Zn-55Al) results in the uniform distribution of the a phase in the microstructure and reduction of non-equilibrium phases. The potentiodynamic polarisation test revealed that an increase in Al in the alloy decreases the corrosion current density. The weight loss test carried out to validate the potentiodynamic test findings exhibited higher weight loss in pure Zn and lowest in Zn-55Al. Similar results were observed in the salt spray test. The multicriteria decision-making analysis revealed that Zn-55Al is the most suitable alloy in a corrosive environment among the tested alloys.

Insight into the corrosion behaviour and degradation mechanism of pure zinc in simulated body fluid

Zn is considered as a promising degradable biomaterial. However, concerns exist for its application as the degradation mechanism of pure Zn in physiological solutions is still not clear. Results indicated that the corrosion product film showed a laminated structure with complex layers, which were ZnO/Zn(OH)2, a Ca/P phase, zinc compounds, and a Ca/P phase from the inside out, respectively. The localized corrosion initiated at grain boundaries and expanded towards the interior of grains with higher corrosion susceptibility, or advanced towards the depth. Additionally, the nature of the corrosion product film and localized corrosion synergistically determined the degradation rate.

Binary Zn–Ti alloys for orthopedic applications: Corrosion and degradation behaviors, friction and wear performance, and cytotoxicity

Zinc (Zn) and its biocompatible and biodegradable alloys have substantial potential for use in orthopedic implants. Nevertheless, pure Zn with a hexagonal close-packed crystal structure has only two independent slip systems, therefore exhibiting extremely low elongation and yield strength in its as-cast condition, which restricts its clinical applications. In this study, as-cast Zn–xTi (titanium) (x = 0.05, 0.10, 0.20, and 0.30 wt.%) binary alloys were hot-rolled and their microstructures, mechanical properties, wear resistance, and cytocompatibility were comprehensively investigated for orthopedic implant applications. The microstructures of both as-cast and hot-rolled Zn–xTi alloys consisted of an α-Zn matrix phase and a TiZn16 phase, while Zn–0.2Ti and Zn–0.3Ti exhibited a finer α-Zn phase due to the grain-refining effect of Ti. The hot-rolled Zn–0.2Ti alloy exhibited the highest yield strength (144.5 MPa), ultimate strength (218.7 MPa), and elongation (54.2%) among all the Zn–xTi alloys. The corrosion resistance of Zn–xTi alloys in Hanks’ solution decreased with increasing addition of Ti, and the hot-rolled Zn–0.3Ti alloy exhibited the highest corrosion rates of 432 μm/y as measured by electrochemical testing and 57.9 μm/y as measured by immersion testing. The as-cast Zn–xTi alloys showed lower wear losses than their hot-rolled counterparts. The extracts of hot-rolled Zn–xTi alloys at concentrations of ≤ 25% showed no cytotoxicity to MG-63 osteosarcoma cells and the extracts of Zn–xTi alloys exhibited enhanced cytocompatibility with increasing Ti content.