Pure Zn Research Articles

High Energy, Long Cycle, and Superior Low Temperature Performance Aqueous Na-Zn Hybrid Batteries Enabled by a Low-Cost and Protective Interphase Film-Forming Electrolyte.

A hybrid aqueous Na-Zn ion battery derived from the Na3V2(PO4)3 cathode is one of the most promising systems among aqueous batteries because it exhibits higher energy density than a pure Zn ion battery due to different ion intercalation mechanisms related to various electrolytes. However, it is more difficult to improve the electrochemical performance of the hybrid aqueous Na-Zn ion battery versus Zn ion battery. In addition, searching for suitable protective interphase film-forming electrolyte additives in order to increase cycling stability and developing a new electrolyte recipe to improve the low temperature performance are significant and still big challenges for the hybrid aqueous Na-Zn battery. Herein, the introduction of protective interphase film-forming additives (VC), an economical 10 M NaClO4-0.17 M Zn(CH3COO)2-2 wt % VC electrolyte, was proposed. Based on such an electrolyte, the carbon-coated single crystalline Na3V2(PO4)3 nanofiber//Zn aqueous Na-Zn hybrid battery involving high energy, long cycle, and outstanding low temperature performance was successfully obtained. For example, it delivered a remarkable output voltage of 1.48 V and excellent cycle stability (retained 84% after 1000 cycles). The capacities were 94.4 mA h/g at 0.2 A/g at -10 °C and 90.0 mA h/g at 0.2 A/g at -20 °C, respectively.

Visible-Light-Active Zn–Fe Layered Double Hydroxide (LDH) for the Photocatalytic Conversion of Rice Husk Extract to Value-Added Products

One of the major causes of excess CO2 in the atmosphere is the direct burning of biomass waste, which can be obviated by the photocatalytic biomass conversion to useful/valuable chemicals/fuels, a sustainable and renewable approach. The present research work is focused on the development of a novel Zn–Fe LDH by a simple co-precipitation method and its utilization for the photocatalytic conversion of a rice husk extract (extracted from rice husk by means of pyrolysis) to value-added products. The synthesized, pure Zn–Fe LDH was characterized by various analytical techniques such as XRD, SEM, FTIR, and UV–Visible DRS spectroscopy. The rice husk extract was converted in a photocatalytic reactor under irradiation with 75 W white light, and the valued-added chemicals were analyzed by gas chromatography–mass spectrometry (GC–MS). It was found that the compounds in the rice husk extract before the photocatalytic reaction were mainly carboxylic acids, phenols, alcohols, alkanes (in a small amount), aldehydes, ketones, and amines. After the photocatalytic reaction, all the carboxylic acids and phenols were completely converted into alkanes by complex reactions. Hence, photocatalytic biomass conversion of a rice husk extract was successfully carried out in the present experimental work, opening new avenues for the development of related research domains, with a great potential for obtaining an alternate fuel and overcoming environmental pollution.

Impact of gadolinium on mechanical properties, corrosion resistance, and biocompatibility of Zn-1Mg-xGd alloys for biodegradable bone-implant applications

Zinc (Zn) and its alloys are currently regarded as one of the promising families of biodegradable metals for implant applications owing to their suitable biodegradability and biofunctionality. However, the inadequate mechanical properties of as-cast (AC) pure Zn restricted the practical clinical bone-implant applications due to its coarse grain size and hexagon close-packed crystal structure. Here, the impact of gadolinium (Gd) on the mechanical properties, corrosion resistance, hemolysis percentage, anticoagulant activity, and cytotoxicity of AC and hot-rolled (HR) Zn-1Mg-xGd (x = 0.1, 0.2, and 0.3) (wt.%) alloys were investigated for biodegradable bone-implant applications. Tensile testing showed that the HR Zn-1Mg-0.3Gd alloy exhibited the highest tensile strength of 288.1 MPa, tensile yield strength of 250.9 MPa, and elongation of 13.2%. Electrochemical corrosion and immersion tests revealed that the corrosion rates of both AC and HR specimens increased with increasing Gd content in Hanks’ solution, and the HR Zn-1Mg-xGd specimens exhibited higher corrosion rates compared to their AC counterparts. The HR Zn-1Mg-xGd specimens showed an increasing hemolysis percentages and decreasing activated partial thromboplastin time (APTT) values with increasing Gd addition. The alloy extracts of HR samples at ≤ 25% concentration exhibited no cytotoxicity toward MG-63 cells, and the HR Zn-1Mg-0.3Gd alloy displayed the highest cell viability among all three alloy extracts at 12.5% concentration. Overall, the HR Zn-1Mg-0.3Gd can be considered a promising biodegradable implant material for bone-implant materials owing to its high mechanical strength and ductility, suitable degradation rate, and satisfying biocompatibility. Statement of significanceIn this work, Zn-1Mg-xGd (x = 0.1, 0.2, and 0.3 wt.%) alloys were developed by alloying with gadolinium (Gd) and hot-rolling, and their mechanical properties, corrosion behavior, hemolysis percentage, anticoagulant activity, and cytotoxicity were investigated for biodegradable implant application. Our findings demonstrated that the hot-rolled Zn-1Mg-0.3Gd alloy exhibit the highest ultimate tensile strength of 288.1 MPa, yield strength of 250.9 MPa, and elongation of 13.2%. Hot-rolled Zn-1Mg-xGd alloys show slowly increasing hemolysis percentages and decreasing activated partial thromboplastin time (APTT) values with increasing Gd addition. Extracts of hot-rolled Zn-1Mg-xGd alloys at a concentration of ≤ 25% show no cytotoxicity towards MG-63 cells, and Zn-1Mg-0.3Gd exhibit good cytocompatibility among all three alloys at a concentration of 12.5%.

Zn–Sn alloy anode with repressible dendrite grown and meliorative corrosion resistance for Zn-air battery

Zinc (Zn) based metal-air battery has been considered as one of promising candidates for the next-generation batteries due to its high theoretical specific capacity and abundant reserve. However, Zn electrode is susceptible to dendrite growth and corrosion depravation in the long cycling process, causing capacity decline and short lifespan. Herein, a novel zinc-stannum (Zn–Sn) alloy electrode has been facilely prepared through powder sintering technology to restrain the dendrite growing and promote the corrosion resistance. Compared with pure Zn foil electrode, the optimized Zn–Sn10 alloy electrode exhibited a lower voltage hysteresis of 119 mV and a better topography with non-dendrite after cycling 400 h at 0.5 mA cm−2. Meanwhile, the Zn corrosion resistance in alkaline electrolyte has been significantly improved. Theoretical calculations also account for these superiorities by the uniform charge distribution in the superficial ZnSn layer. As a result, the assembled Zn-air battery based on Zn–Sn alloy anode electrode showed satisfactory power density, rate properties and cycling life. This research provides a facile and cost-efficient strategy to stabilize Zn anode and holds great promise in developing high-performance rechargeable Zn-based battery energy systems.

Calorimetric study of Zn13La

Abstract The thermodynamic properties of Zn13La were investigated by calorimetry. The standard entropy of formation at 298 K, Δ f S 298 ° ${{\Delta }_{\text{f}}}S_{298}^{{}^\circ }$ was determined from measuring the heat capacities, Cp , from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, Δ f H 298 ° ${{\Delta }_{\text{f}}}H_{298}^{{}^\circ }$ was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, Δ f G 298 ° ${{\Delta }_{\text{f}}}G_{298}^{{}^\circ }$ was determined from these data. The coefficient, γ, of the electronic term contributing to the heat capacity of Zn13La was similar to the composition average of the values of pure Zn and La, indicating that the 5d- and 4f-electron states for La are localized in the vicinity of the Fermi energy level.

Calorimetric study of MgZn2 and Mg2Zn11

Abstract The thermodynamic properties of MgZn2 and Mg2Zn11 were investigated by calorimetry. The standard entropies of formation at 298 K, Δ f S 298 ° $\Delta _{\rm{f}} S_{298}^{\rm{^\circ }} $ were determined from measuring the heat capacities, Cp , from near absolute zero (2 K) to 390 K by the relaxation method. The standard enthalpies of formation at 298 K, Δ f H 298 ° $\Delta _{\rm{f}} H_{298}^{\rm{^\circ }} $ were determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energies of formation at 298 K, Δ f G 298 ° $\Delta _{\rm{f}} G_{298}^{\rm{^\circ }} $ were determined from these data. The electronic contribution to the heat capacities of MgZn2 and M2Zn11 were found to be similar to pure Zn, indicating that the valence electrons of Mg are trapped by the density of states for Zn in the vicinity of the Fermi level.

Developing sustainable Zn-MWCNTs composite coatings using electrochemical co-deposition method: Tribological and surface wetting behavior

ABSTRACT Carbon nanotube (CNT) nanofillers are a part of carbon allotrope family materials with numerous and effective features. Multiple CNTs nested one another is a low-cost and scalable category of CNTs, known as multi-walled CNTs (MWCNTs), which are well-stablised for their excellent mechanical, electrical and thermal properties. In this present work, MWCNTs nanofiller embedded Zn matrix (Zn-MWCNTs) composite coatings were fabricated by adding the different concentrations of MWCNTs (0.5, 0.1 and 0.2 g/L) in the acidic electrolyte bath using electrochemical co-deposition route with uniform embedment. The prepared composite coatings were characterised using advanced characterisation techniques (XRD, FESEM and EDS) for their obtained surface morphology and microstructures. All Zn-MWCNTs composite coatings exhibited enhanced tribo-mechanical performance compared to pure Zn coatings. Zn-MWCNT (0.2 g/L) composite coating exhibited the highest average microhardness value of 119 HV and minimum wear rate of 12.5 × 10−3 mm3N−1m−1 among all the prepared composite coatings, which attributed to the synergistic effect of microstructural refinement and superior mechanical properties of MWCNTs. Surface wetting studies reveal that MWCNTs play an important role in increasing hydrophobicity in terms of contact angle, which increased by 1.93 times for Zn-MWCNT (0.2 g/L) composite coating. The present work may be helpful for facile fabrication of low-cost biocidal Zn-MWCNTs nanocomposite coating.

Feasibility evaluation of a Zn-Cu alloy for intrauterine devices: In vitro and in vivo studies

The comprehensively adopted copper-containing intrauterine devices (Cu-IUDs) present typical adverse effects such as bleeding and pain at the initial stage of post-implantation. The replacement of Cu material is demanded. Zinc and its alloys, the emerging biodegradable materials, exhibited contraceptive effects since 1969. In this work, we evaluated the feasibility of bulk Zn alloys as IUD active material. Using pure Cu and pure Zn as control groups, we investigated the contraceptive performance of Zn-0.5Cu and Zn-1Cu alloys via in vitro and in vivo tests. The results showed that the main corrosion product of Zn-Cu alloys is ZnO from both in vitro and in vivo studies. CaZn2(PO4)2·2H2O is formed atop after long-term immersion in simulated uterine fluid, whereas CaCO3 is generally formed atop after implantation in the rat uterine environment. The cytocompatibility of the Zn-1Cu alloy was significantly higher than that of the pure Zn and pure Cu to the human endometrial epithelial cell lines. Furthermore, the in vivo results showed that the Zn-1Cu alloy presented much improved histocompatibility, least damage and the fastest recovery on endometrium structure in comparison to pure Zn, Zn-0.5Cu and pure Cu. The systematic and comparing studies suggest that Zn-1Cu alloy can be considered as a possible candidate for IUD with great biochemical and biocompatible properties as well as high contraceptive effectiveness. Statement of significanceThe existing adverse effects with the intrinsic properties of copper materials for copper-containing intrauterine devices (Cu-IUD) are of concerns in their employment. Such as burst release of cupric ions (Cu2+) at the initial stage of the Cu-IUD. Zinc and its alloys which have been emerging as a potential biodegradable material exhibited contraceptive effects since 1969. In this study, Zn-1Cu alloys displayed significantly improved biocompatibility with human uterus cells and a decreased inflammatory response within the uterus. Therefore, high antifertility efficacy of the Zn-1Cu alloy was well maintained, while the adverse effects are significantly eased, suggesting that the Zn-1Cu alloy is promising for IUD.

Fabrication and Properties of Zn-3Mg-1Ti Alloy as a Potential Biodegradable Implant Material.

A Zn-3Mg-1Ti alloy was fabricated by ultrasonic treatment of Zn-Mg alloy melt using a Ti ultrasonic radiation rod. The microstructure, phase structure, mechanical properties, degradation property, and in vitro cytotoxicity were investigated systematically. The obtained Zn-3Mg-1Ti alloy is composed of the Zn, Mg2Zn11, and TiZn16. Owing to the grain refinement and second phase reinforcement, the mechanical properties of Zn-3Mg-1Ti alloy is improved. In addition, the Zn-3Mg-1Ti alloy exhibits minimal cytotoxicity compared to pure Zn and Zn-1Ti alloy. Electrochemical tests show that the Zn-3Mg-1Ti alloy has an appropriate degradation rate in Hank’s solution.

Diffusion Bonding of Al-Mg-Si Alloy and 301L Stainless Steel by Friction Stir Lap Welding Using a Zn Interlayer.

Friction stir lap welding (FSLW) is expected to join the hybrid structure of aluminum alloy and steel. In this study, the Al-Mg-Si aluminum alloy and 301L stainless steel were diffusion bonded by FSLDW with the addition of 0.1 mm thick pure Zn interlayer, when the tool pin did not penetrate the upper aluminum sheet. The characteristics of lap interface and mechanical properties of the joint were analyzed. Under the addition of Zn interlayer, the diffusion layer structure at lap interface changed from continuous to uneven and segmented. The components of the diffusion layer were more complex, including Fe-Al intermetallic compounds (IMCs), Fe-Zn IMCs and Al-Zn eutectic. The largely changed composition and thickness of uneven and segmented diffusion layer at the lap interface played a significant role in the joint strength. The tensile shear load of Zn-added joint was 6.26 kN, increasing by 41.3% than that of Zn-not-added joint. These two joints exhibited interfacial shear fracture, while the Zn interlayer enhanced the strength of diffusion bonding by extending the propagation path of cracks.

Effect of Ni Concentration on the Surface Morphology and Corrosion Behavior of Zn-Ni Alloy Coatings

This research work aims to develop electrodeposited Zn-Ni alloy coatings with controlled dissolution tendencies on a mild steel substrate. The varying Ni concentration in the electroplating bath, i.e., 10, 15, 20 and 25 g·L−1, affected the surface morphology and electrochemical properties of the deposited Zn-Ni alloy coatings. SEM and EDS analysis revealed the resulting variation in surface morphology and composition. The electrochemical behavior of different coatings was evaluated by measuring the open circuit potential and cyclic polarization trends in 3.5 wt.% NaCl solution. The degradation behavior of the electrodeposited Zn-Ni coatings was estimated by conducting a salt spray test for 96 h. The addition of Ni in the coating influenced the coating thickness and surface morphology of the coatings. The coating thickness decreased from 38.2 ± 0.5 μm to 20.7 ± 0.5 μm with the increase in Ni concentration. Relatively negative corrosion potential (<−1074 ± 10 mV) of the Zn-Ni alloy coatings compared to the steel substrate (−969 mV) indicated the sacrificial dissolution behavior of the Zn-rich coatings. On the other hand, compared to the pure Zn (26.12 mpy), ~4 times lower corrosion rate of the Zn-Ni coating (7.85 mpy) was observed by the addition of 25 g·L−1 Ni+2 in the bath solution. These results highlighted that the dissolution rate of the sacrificial Zn-Ni alloy coatings can effectively be tuned by the addition of Ni in the alloy coating during the electrodeposition process.

Local pH and oxygen concentration at the interface of Zn alloys in Tris-HCl or HEPES buffered Hanks’ balanced salt solution

Although Tris-HCl and HEPES are typically used pH buffers for in vitro studies, they are recently proven to be unable to stabilize local pH at Mg interface in simulated body fluids. In this study, local pH close to physiological (7.1–7.5) was found at metal/fluid interface of pure Zn, Zn-0.8 wt%Ca and Zn-0.8 wt%Mg alloys in Tris-HCl or HEPES buffered Hanks’ balanced salt solution (HBSS) at 37 °C under hydrodynamic conditions. High rate oxygen consumption was detected above Zn alloys in various HBSS electrolytes. These findings support the previous recommendation of using synthetic pH buffers for in vitro studies of biodegradable Zn-based alloys.

Stress Corrosion Analysis and Direct Cell Viability of Biodegradable Zn-Fe-Ca Alloy in In-Vitro Conditions

Due to the excellent biocompatibility of Zn and Zn-based alloys, researchers have shown great interest in developing biodegradable implants based on zinc. Furthermore, zinc is an essential component of many enzymes and proteins. The human body requires ~15 mg of Zn per day, and there is minimal concern for systemic toxicity from a small zinc-based cardiovascular implant, such as an arterial stent. However, biodegradable Zn-based implants have been shown to provoke local fibrous encapsulation reactions that may isolate the implant from its surrounding environment and interfere with implant function. The development of biodegradable implants made from Zn-Fe-Ca alloy was designed to overcome the problem of fibrous encapsulation. In a previous study made by the authors, the Zn-Fe-Ca system demonstrated a suitable corrosion rate that was higher than that of pure Zn and Zn-Fe alloy. The Zn-Fe-Ca system also showed adequate mechanical properties and a unique microstructure that contained a secondary Ca-reach phase. This has raised the promise that the tested alloy could serve as a biodegradable implant metal. The present study was conducted to further evaluate this promising Zn alloy. Here, we assessed the material’s corrosion performance in terms of cyclic potentiodynamic polarization analysis and stress corrosion behavior in terms of slow strain rate testing (SSRT). We also assessed the ability of cells to survive on the alloy surface by direct cell culture test. The results indicate that the alloy develops pitting corrosion, but not stress corrosion under phosphate-buffered saline (PBS) and air environment. The direct cell viability test demonstrates the successful adherence and growth of cells on the alloy surface.

Hardness and corrosion resistance of Zn−Mn/Al2O3 composite coatings produced by electrochemical deposition

The aim of this study is development and characterization of the novel Zn-Mn/Al2O3 composite coatings. The coatingswere electrodeposited with constant current density on steel, from chloride solution, without any commercial additives. TheZn−Mn alloy coatings that show high corrosion resistance, may be used in future as an alternative to cadmium coatings.However, the pure Zn and Zn alloy coatings are characterized with poor mechanical properties. Therefore, in this work thealumina particles were incorporated into the Zn-Mn matrix, and the hardness and corrosion resistance of the obtainedcomposite coatings were tested. The mechanical and ultrasound agitation were used to achieve good dispersion of platingsolution and homogeneous co-deposition of second phase. The goal was to examine the effect of the agitation type in bath,on the attributes of the deposited composite coatings. The incorporation of Al2O3 particles was enhanced when themechanical agitation of the solution was applied. However, in case that this agitation method was used, the agglomeration ofthe alumina particles occurred. In contrast, when an ultrasonic agitation of the plating solution was applied, the uniformdistribution of the alumina particles could be achieved. The presence of particles in the matrix, along with appliedultrasound, resulted in grain refinement and homogeneous microstructure. The Al2O3 nanoparticles incorporated in Zn-Mnalloy matrix, resulted in a significant increment in the indentation hardness and a modest increase in the coating corrosionresistance. However, the coating hardness increased with alumina addition, only in case when an ultrasonic agitation of theelectrodeposition solution was used.

Optoelectronic properties and Effect of annealing on structural of Zn mixed CdS thin film by SILAR method

In this research, the zinc mixed cadmium sulfide thin films were synthesized on the glass substrate by simple and easy successive ionic layer adsorption and reaction (SILAR) process. The thin films were prepared by different mixing percentage of Zinc with cadmium sulfide. The Zn-CdS films have been characterized by X-Ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and optical properties were investigated by ultraviolet-visible spectrophotometer. X-Ray studies show the hexagonal crystal structure of CdS film. The surface morphology is found different in both annealed and unannealed structure from FESEM image. It is smooth, dense and uniform in structure in case of unannealed condition. And it is non-uniform structure when annealed. The absorbance spectra of pure CdS and Zn mixed CdS has compared and it is observed that Zn-mixed CdS have greater absorbance than pure CdS.

Anion exchange separations to produce a suitable electrolyte for the electrodeposition of pure zinc

Anion exchange separations have been devised to purify model solutions of the usual pickling liquor (SPL) obtained from hot dip galvanization to produce a suitable ZnCl2 electrolyte for electrodepositing pure Zn. The method was based on the established anion-exchange distribution functions in chloride media. Both the simple batch and the more accurate chromatographic methods of separation were examined. The loaded solutions contained Zn, Fe, Mn, Ni and Pb of different concentrations with 1.8 - 2 M NaCl or HCl as the background. The resin bed primarily retained Zn while divalent Fe, Mn and Ni were removed in the loading and the continued rinsing steps with the mobile phase at the initial level of Cl- ion concentration. The elution of Zn was carried out by a significantly reduced Cl- ion concentration. The preliminary reduction of the iron to its divalent state was found of utmost importance. The only difficulty arises from the separation of Pb, which has an equilibrium distribution function comparable to the anion exchange of Zn, however in Europe this minor impurity should not be present at disturbing levels. Kinetic examination of the batch process revealed that Zn sorption is virtually complete within 20 minutes, however despite the low distribution coefficients, some 10 % of iron is also sorbed. Almost 90 % of the retained iron could be in the Fe(III) state caused by aerial oxidation. It was also found that the elution of Zn in the batch technique was not possible by just lowering the Cl- ion concentration. Therefore, the chromatographic method is the only possible way if only chloride media are to be applied.

Additive manufacturing of Zn with submicron resolution and its conversion into Zn/ZnO core-shell structures.

Electrohydrodynamic redox 3D printing (EHD-RP) is an additive manufacturing (AM) technique with submicron resolution and multi-metal capabilities, offering the possibility to switch chemistry during deposition "on-the-fly". Despite the potential for synthesizing a large range of metals by electrochemical small-scale AM techniques, to date, only Cu and Ag have been reproducibly deposited by EHD-RP. Here, we extend the materials palette available to EHD-RP by using aqueous solvents instead of organic solvents, as used previously. We demonstrate deposition of Cu and Zn from sacrificial anodes immersed in acidic aqueous solvents. Mass spectrometry indicates that the choice of the solvent is important to the deposition of pure Zn. Additionally, we show that the deposited Zn structures, 250 nm in width, can be partially converted into semiconducting ZnO structures by oxidation at 325 °C in air.

A smelting-rolling strategy for ZnIn bulk phase alloy anodes.

Reversibility and stability are considered as the key indicators for Zn metal anodes in aqueous Zn-ion batteries, yet they are severely hindered by uncontrolled Zn stripping/plating and side reactions. Herein, we fabricate a bulk phase ZnIn alloy anode containing trace indium by a typical smelting-rolling process. A uniformly dispersed bulk phase of the whole Zn anode is constructed rather than only a protective layer on the surface. The Zn deposition can be regarded as instantaneous nucleation due to the adsorption of the evenly dispersed indium, and formation of the exclusion zone for further nucleation can be prevented at the same time. Owing to the bulk phase structure of ZnIn alloy, the indium not only plays a crucial role in Zn deposition, but also improves the Zn stripping. Consequently, the as-designed ZnIn alloy anode can sustain stable Zn stripping/plating for over 2500 h at 4.4 mA cm-2 with nearly 6 times smaller voltage hysteresis than that of pure Zn. Moreover, it enables a substantially stable ZnIn//NH4V4O10 battery with 96.44% capacity retention after 1000 cycles at 5 A g-1. This method of regulating the Zn nucleation by preparing a Zn-based alloy provides a potential solution to the critical problem of Zn dendrite growth and by-product generation fundamentally.

Resistance Spot Weld Ability of Mild Steel Coated with Zn, Galfan and ZA12

In this study, the weldability of mild steel coated with different Zn-based materials to prevent corrosion with resistance spot welding process was investigated. For this purpose, the surfaces of mid steel were coated with pure Zn, Galfan (Zn5Al) and ZA12 (Zn11Al1Cu) alloys. Hot dipping technique was used for coating. Mild steels with dimension of 1.5X15X40 mm were immersed in the melted Zn and alloys, and the surfaces were coated by waiting for 2 minutes. Steel and coated steel pairs were joined by resistance spot welding process. The welding interface microstructures were examined under light optical microscopy (LOM). Weld interface strengths were measured by axial shear tests. The tests were performed at the room temperature and with a tensile speed of 5mmmin-1. Microstructure investigations showed a good bonding occurred between the coating and the steel and between the welded materials. Mechanical tests have shown that coating the steel reduces the weld strength and the decrease in strength continues with the increase of alloying elements in the coating.

Hot-extrusion behavior of biodegradable Zn-Mg alloys

Magnesium, zinc and iron-based alloys are the potential candidates for biodegradable implant applications and the effect of secondary processing on the biodegradability of these materials is of interest and being studied extensively. The evolution of gaseous hydrogen in magnesium-based alloys and higher corrosion rate limits the usage of these alloys, whereas, on the other hand, iron alloy's corrosion rate is too slow and leaves bulky corrosion products. The corrosion rate of Zn is in between the Mg and Fe, make it a potential alternate material. In the present study, pure Zn and Zn-Mg alloys are cast to different weight proportions and subjected to hot extrusion at different temperatures viz: 100, 150, 200, 250 and 300 °C. No surface defects were observed during extrusion of Zn at all temperatures, whereas Zn-Mg alloys were found to exhibit surface cracks at all temperatures except 200 and 250 °C. The presence of longitudinal tensile stresses at the surface due to frictional forces and inappropriate temperatures resulted in the development of cracks. The extruded samples were found to have fine microstructure as observed through an optical microscope. The XRD studies revealed the presence of the Mg2Zn11phase. The hardness of Zn was observed to increase by 26% after hot-extrusion which was due to the extensive grain refinement during extrusion.