Pure Zn Research Articles

High-Efficient Vacuum Ultraviolet-Ozone Assist-Deposited Polydopamine for Poly(lactic-co-glycolic acid)-Coated Pure Zn toward Biodegradable Cardiovascular Stent Applications.

Zinc is a prospective metal for biodegradable cardiovascular stent applications, but the excessively released Zn2+ during degradation remains a huge challenge in biocompatibility. Considerable efforts have been made to develop a high-efficient surface modification method, while maintaining adhesion strength, mechanical support, and vascular compatibility. Biomimetic polydopamine (PDA) can adhere to Zn tightly, subsequently achieving robust chemical bonds with poly(lactic-co-glycolic acid) (PLGA) coating. However, the deposition of PDA on Zn depends on the controlled conditions such as a sensitive pH and a long period of time. Herein, we introduce vacuum ultraviolet-ozone (VUV/O3) assist-deposition technology to accelerate the polymerization of PDA on pure Zn, which shortens the process to 40 min at a moderate pH of 8.5 and improves the deposition rate by 1-2 orders of magnitude under sufficient active oxygen species (ROS). Additionally, PLGA/PDA coating enhances the corrosion resistance, and their effective protection maintains the mechanical properties after long-term corrosion. Moreover, the controlled Zn2+ release contributes to the superior in vitro biocompatibility, which inhibits the hemolysis rate and smooth muscle cell (SMC) proliferation. The enhanced endothelial cell (EC) proliferation is promising to promote the re-endothelialization, avoiding in-stent restenosis and neointimal hyperplasia. Such modified Zn might be a viable candidate for the treatment of cardiovascular diseases.

Biodegradable Zn–Sr alloys with enhanced mechanical and biocompatibility for biomedical applications

Zinc (Zn) is a new generation of biodegradable metal as temporary biomedical implants with a promising degradation rate. However, its clinical applications have been limited because of the insufficient mechanical properties. Considering the degradation property and biocompatibility, we proposed Zn–Sr alloys after extrusion treatments to simultaneously improve the mechanical strength and ductility. The in vitro and in vivo degradation and biocompatibility were also evaluated using electrochemical and immersion corrosion tests, various cell and bacterial models, together with subcutaneous and femoral implantations in rats. Results showed that the extruded Zn-0.7Sr alloys exhibited two times higher mechanical strengths (∼120 ​MPa) and better ductility (∼10%) than the pure Zn counterparts. The Zn–Sr alloys provided enhanced in vitro and in vivo biocompatibility along with promising antibacterial properties.

Experimental investigation and empirical modeling for corrosion rate prediction of biodegradable zinc based composite considering the effect of constituent materials

Biodegradable zinc (Zn) has shown great potential in the area of biomedical applications. Though, the mechanical properties are decisive for the use of Zn for orthopedic and cardiovascular applications. Consequently, one needs to focus on improving the mechanical properties of Zn for its suitability in biomedical applications. Alloying of essential elements of the human body resulted in enhancement of Zn’s mechanical properties in recent years. The corrosion rate of pure Zn is ideal; however, the addition of other elements has resulted in a loss of its ideal corrosion rate. The inclusion of hydroxyapatite (HA) and iron (Fe) in Zn has also been reported in improving the mechanical properties. Hence, a need is raised for the development of a model which can predict the corrosion rate after adding HA along with Fe in Zn. In this research work, empirical based modeling is proposed to predict the corrosion rate, which incorporates the outcome of addition of Fe and HA in Zn. The Zn based materials were fabricated with the help of microwave sintering for developing the empirical model. The corrosion properties of the materials were assessed through a potentiodynamic polarization test in a simulated body fluid solution. The enhanced corrosion rate was attained with the rise in HA (wt%) and Fe (wt%) in Zn. An empirical correlation was established between the influencing controlling parameters (i.e., corrosion current, equivalent weight, and material density) of corrosion rate. Confirmation experiments were conducted to validate the developed model, and the highest error of 6.12% was obtained between the experimental and predicted values exhibiting the efficaciousness of the proposed model.

New resorbable Ca-Mg-Zn-Yb-B-Au alloys: Structural and corrosion resistance characterization

New resorbable Ca32Mg12Zn38Yb18-2xBxAux (x = 1,2) alloys were designed and prepared in order to verify their use for medical applications as potential short-term implants. Their amorphous structure containing some crystalline phases (CaZn, CaZn2 and MgZn) was determined by X-ray and neutron diffraction and electron microscopy methods. The biocorrosion behavior of the plates was tested by hydrogen evolution measurements, immersion, electrochemical polarization tests, and electrochemical impedance spectroscopy in Ringer's solution at 37 °C. The corrosion analysis was also supplemented by X-ray diffraction, photoelectron, and ICP-AES spectroscopy. The corrosion resistivity measurements revealed that the alloys manifest enhanced corrosion resistance. The corrosion current density for Ca32Mg12Zn38Yb18-2xBxAux (x = 1, 2) alloys were 18.46 and 8.79 μA/cm2, which is lower than for pure Mg (47.85 μA/cm2) and Zn (33.96 μA/cm2). A decreasing tendency for hydrogen to evolve as a function of time was noted. The hydrogen evolution did not exceed 1 ml/cm2 over 1 h and average corrosion rate is calculated as 0.32 g/m2 . h for Ca32Mg12Zn38Yb14B2Au2 alloy after 312 h. The corrosion mechanism of the alloys includes an anodic dissolution, a hydroxide precipitation, corrosion product layer formation and corrosion propagation stage.

Biomedical potential of 3D Zn and ZnCu foams produced by dynamic hydrogen bubble template

New biomaterials for bone healing applications are crucial for our ageing populations. Three-dimensional (3D) Zn and ZnCu architectures on stainless steel were reinvented through dynamic hydrogen bubble template (DHBT) deposition. 3D Zn was formed by porous pure Zn structures, whereas an interconnected architecture composed of CuxZny was detected in ZnCu foams, with the preferential deposition of Cu on the top and Zn on the bottom. These materials, with pore diameters ranging from 0.4 to 5 µm in 3D Zn and from 60 to 270 µm in ZnCu foams, have applications in drug delivery or scaffold systems, respectively. To evaluate the biomedical usage of these materials, their degradation in different biological media was assessed. Both materials were stable in cell culture medium and active in simulated body fluid solution, where typical Cu- and Zn-derived corrosion products were formed. The bioactivity of the degradation products formed, namely Zn and Cu oxides, hydrozincite, simonkolleite and hydroxyapatite, all most likely doped with Cu in the ZnCu foams, was related to their applicability in the biomedical field. Based on these findings, 3D Zn and ZnCu foams produced by DHBT proved their biomedical potential, an original approach reported herein for the first time.

A Study on the Self-Discharge Behavior of Zinc-Air Batteries with CuO Additives

Zn-air batteries have promise as the next generation of batteries. However, their self-discharge behavior due to the hydrogen evolution reaction (HER) and corrosion of the Zn anode reduce their electrochemical performance. Copper (II) oxide (CuO) effectively suppresses the corrosion and HER. In addition, different electrochemical behavior can be obtained with different shape of nano CuO. To improve the performance of Zn-air batteries, in this study we synthesized nano CuO by the hydrothermal synthesis method with different volumes of NaOH solutions. Materials were characterized by XRD, FE-SEM, and EDX analysis. The sphere-like nano CuO (S-CuO) showed a specific discharge capacity of 428.8 mAh/g and 359.42 mAh/g after 1 h and 12 h storage, respectively. It also showed a capacity retention rate of 83.8%. In contrast, the other nano CuO additives showed a lower performance than pure Zn. The corrosion behavior of nano CuO additives was analyzed through Tafel extrapolation. S-CuO showed an Icorr of 0.053 A/cm2, the lowest value among the compared nano CuO materials. The results of our comparative study suggest that the sphere-like nano CuO additive is the most effective for suppressing the self-discharge of Zn-air batteries.

Silver-enriched ZnO:Ag thin films deposited by magnetron co-sputtering: Post annealing effects on structural and physical properties

The ZnO semiconductor is probably among the most mentioned compounds in the scientific literature during the last decade, which is mainly due to its wide spectrum of applications. Compounds based on ZnO (in doped or composite form) are of great relevance for the development of high-tech devices. In this work, we present the growth and characterization of samples deposited by DC Magnetron co-sputtering from two pure Zn and Ag targets in an O2 / Ar atmosphere. The samples were characterized as deposited and after an annealing treatment in a reducing atmosphere. We have used XRD, RBS, ellipsometry, UV visible photoluminescence, and electrical measurements for sample characterization. The results revealed the amorphization of ZnO when the Ag content increases and, after annealing, a mixture of crystalline phases was detected for the samples with higher Ag content. It is also demonstrated the strong effect of the presence of Ag atoms in the stimulated optical and electrical responses from ZnO:Ag compounds obtained in this work.

Long-term in vitro corrosion behavior of Zn-3Ag and Zn-3Ag-0.5Mg alloys considered for biodegradable implant applications

In this paper, Zn-3Ag and Zn-3Ag-0.5Mg alloys were studied in terms of applicability as biodegradable implant materials. The performed tensile, compression and bending tests indicate a high strengthening effect induced by the Ag and Mg additions, additionally resulting in grain size refinement. It was shown that sustaining plastic strain during deformation depends on the applied stress causing asymmetric mechanical behavior of the tested Zn-based materials. Electrochemical measurements and immersion tests in Hanks' solution lasting up to 180 days revealed that Ag and Mg contribute to the change of the Zn matrix's open circuit potential and the formation of micro-galvanic cells between the Zn grains and precipitates. The fine-grained microstructure and evenly distributed small precipitates led to uniform corrosion occurring via pit formation on the corroded surface due to intergranular and micro-galvanic corrosion mechanisms. The corrosion rate of the Zn-3Ag-0.5Mg alloy after 180 days was almost twice that of pure Zn and the Zn-3Ag alloy.

Basal-plane stacking fault energies of biodegradable Zn-based alloys: A first-principles study of alloying effects

Generalized stacking fault energies (GSFEs) associated with the basal planes of pure Zn and substitutional Zn47X (X = Li, Mg, Al, Ti, Mn, Fe, Cu or Ag) were investigated by first-principles calculations in combination with climbing-image nudged elastic band (CINEB) methods. The transition elements, including Ti, Mn and Fe, were found to have relatively strong ability to increase the stability of I2 stacking fault by forming strong interatomic bonding with surrounding Zn atoms. To develop biodegradable Zn-based alloys with superior mechanical properties, especially improved creep properties, Ti, Mn or Fe is recommended as a proper alloying element.

Investigation on tribological behaviors of biodegradable pure Zn and Zn-X (Li, Cu, Ge) binary alloys

As a potential biodegradable implant material, zinc (Zn) alloys have attracted increasing attention due to their good biocompatibility and moderate degradation rate. Zn and its alloys are expected to become candidate materials for medical devices. The metals implanted in the human body will inevitably undergo friction in the human body before it is completely degraded. Friction and wear are essential factors which may cause medical devices’ service failure. However, there are still few studies on the friction and wear properties of biodegradable Zn-based alloys in the human body, and most studies just focus on the mechanical properties, degradation properties and biocompatibility of the alloys. Thus, it is crucial to study the friction and wear properties of Zn and its alloys. In the present work, we investigated the tribological properties of biodegradable pure Zn and Zn-X (Li, Cu, Ge) alloys. Our study found that under simulated body fluid and dry friction conditions, the addition of alloying elements Li and Cu can improve the friction properties of Zn. Among the four metals, Zn-0.5Li alloy has the lowest friction coefficient and the best wear resistance. Hank’s solution has lubricating and corrosive effects. That is to say, when the alloy is rubbed in Hank’s solution, it can not only be protected by the lubrication of the solution, but also tribocorrosion will occur as well.

Corrosion and Biocompatibility of Pure Zn with a Micro-Arc-Oxidized Layer Coated with Calcium Phosphate

Recent studies have indicated a great demand to optimize the biocompatibility properties of pure Zn as an implant material. For this purpose, CaZn2(PO4)2·2H2O (CaZnP) was prepared using hydrothermal treatment (HT) combined with micro-arc oxidation (MAO) on pure Zn substrate to generate biodegradable implants. The polarization test and electrochemical impedance spectroscopy indicated that the MAO1−HT coating could modulate the corrosion behavior of MAO1 by filling the crevice between the coating and the substrate. Immersion test evaluation revealed that the osteogenic properties of MAO1−HT coating were better than that of pure Zn substrate, as evidenced by the molar ratio of Ca and P, which increased after soaking in simulated body fluid (SBF) for up to 10 days. In addition, L-929 cells cultured in the 100%, 50%, and 25% extracts of MAO1−HT coated samples exhibited excellent cytocompatibility. Meanwhile, cell adhesion was promoted on the surface with high roughness generated during MAO and HT processes. In summary, the calcified coatings improved biocompatibility and adjusted the degradation rates of pure Zn, broadening the application of Zn alloys.

Feasibility evaluation of a Cu-38 Zn alloy for intrauterine devices: In vitro and in vivo studies

The existing adverse effects of copper in copper-containing intrauterine devices (Cu-IUDs) have raised concerns regarding their use. These adverse effects include burst release of cupric ions (Cu2+) at the initial stage and an increasingly rough surface of the Cu-IUDs. In this study, we investigated the use of two copper alloys, Cu-38 Zn and H62 as the new upgrading or alternative material for IUDs. Their corrosive properties were studied in simulated uterine fluid (SUF) by using electrochemical methods, with pure Cu as a control. We studied the in vitro long-term corrosion behaviors in SUF, cytotoxicity to uterine cells (human endometrial epithelial cells and human endometrial stromal cells), in vivo biocompatibility and contraceptive efficacy of pure Cu, H62, and Cu-38 Zn. In the first month, the burst release rate of Cu2+ in the Cu-38 Zn group was significantly lower than those in the pure Cu and H62 groups. The in vitro cytocompatibility Cu-38 Zn was better than that of pure Cu and H62. Moreover, Cu-38 Zn showed improved tissue biocompatibility in vivo experiments. Therefore, the contraceptive efficacy of the Cu-38 Zn is still maintained as high as the pure Cu while the adverse effects are significantly eased, suggesting that Cu-38 Zn can be a suitable potential candidate material for IUDs. Statement of significanceThe existing adverse effects associated with the intrinsic properties of copper materials for copper-containing intrauterine devices (Cu-IUD) are of concern in their employment. Such as, burst release of cupric ions (Cu2+) at the initial stage and an increasingly rough surface of the Cu-IUD. In this work, Cu alloyed with a high amount of bioactive Zn was used for a Cu-IUD. The Cu-38 Zn alloy exhibited reduced burst release of Cu2+ within the first month compared with the pure Cu and H62. Furthermore, the Cu-38 Zn alloy displayed significantly improved biocompatibility and a much smoother surface. Therefore, high antifertility efficacy of the Cu-38 Zn alloy was well maintained, while the adverse effects are significantly eased, suggesting that the Cu-38 Zn alloy is promising for a Cu-IUD.

ZnSn nanocatalyst: Ultra-high formate selectivity from CO2 electrochemical reduction and the structure evolution effect

The introduction of tin (Sn) into Zn-based catalyst can change its intrinsic properties of the electrochemically reduction of CO2 to CO, obtaining a high formate yield. The electron transfer from Zn to Sn lowers down the d-band center of Sn, leading to a more reliable surface adsorption of the *OCHO intermediate and high formate selectivity. The obtained ZnSn catalyst enables formate formation with a drastically boosted Faradaic efficiency (FE) up to 94%, which is 2.04 and 1.34 times of pure Zn and Sn foils, respectively, indicating a synergistic effect between Zn and Sn. During the electrochemical CO2 reduction reaction (eCO2RR) process, the morphology of the ZnSn catalyst evolved from nanoparticles to nanosheets, nanoneedles and collapsed structures, corresponding to the activation, stabilization and decay stages, respectively. This study provides a facile and controllable approach for the construction of novel bimetallic catalyst favoring formate selectivity based on the synergistic effect.

Structural, dielectric, impedance, complex modulus, and optical study of Ni-doped Zn(1−x)NixO nanostructures at high temperatures

This experiment addressed the effect of Nickel-doped on the dielectric, ac conductivity, and optical properties of pure and doped Zn (1−x) Nix O (x = 0, 3 and 6%) nanostructures. The un-doped and Ni-doped ZnO nanostructures were synthesized using co-precipitation. In this paper, the frequency-dependent dielectric and the electrical conductivity of un-doped and Ni-doped Zn (1−x) Nix O nanostructures were examined at various temperatures ranging from 320 K to 460 K using an LCR meter. For the morphological and optical investigation, the prepared samples were analyzed using field emission-scanning electron microscopy (FE-SEM), and UV visible Spectroscopy was used at room temperature. The dielectric constant (), dielectric loss (), tangent loss (tan δ), the real as well as the imaginary part of the impedance against the frequency ranging from 100 Hz to 2 × 106 Hz that declines with increases in frequency at different temperatures ranging from 320–460 K. However, the electrical conductivity () increased with the increase in frequency was examined. The ac conductivity () follows Jonscher,s power law that the electrical conductivity is enhanced with increasing doping concentration. The optical transmission area also improved due to an increase in Ni-doping concentration in ZnO. The optical bandgap of pure and Ni-doped ZnO nanostructures is in the range lies 3.30–3.12 eV found that to decrease with the increase in Ni doping concentrations.

Microstructure, mechanical properties, and biodegradation response of the grain-refined Zn alloys for potential medical materials

As a new kind of biodegradable metal, Zn possesses promising features, i.e. suitable biodegradability and biocompatibility, lower energy consumption for melting, better recyclability, and processing size tolerance. Such features provide some new insights for manufacturing medical implants. However, cast pure Zn usually contains coarsening microstructures, which brings about poor syngenetic controlling between mechanical strength and degradation rate. In the present work, a significant grain refinement was achieved in the Zn alloys through combination of solidification and rolling, followed by exploration of the mechanical response and in vitro degradation. Specifically, the grain refiner (i.e. Zn–Al master alloy) was firstly prepared and, then, added into cast pure Zn during solidification. Fine equiaxed grains were obtained due to the constitutional supercooling (CS)-driven interdependence effects. Then, the cast Zn alloys were subjected to hot rolling at 200 °C, which gives rise to further reduction in the grain size of Zn alloys. Thereafter, the mechanical properties and the in vitro immersion testing were carried out not only in the as-rolled Zn–Al alloys, but also in the purely cast Zn–Al alloys for comparison. The {0001} basal plane texture became dominant in all the as-rolled Zn–Al alloys; however, the weak {112¯0} prismatic plane texture occurred in the high alloying Zn–Al alloys (>1.5wt% Al). Finally, the mechanisms behind the mechanical improvement and the in vitro degradation were discussed. These work shield new light on synergic tunning between the biodegradable rate and mechanical strength of Zn alloys.

A Mg alloy with no hydrogen evolution during dissolution

Hydrogen evolution is normally associated with the corrosion or dissolution of Mg alloys in aqueous solutions. This work studied the corrosion behavior of sputtered pure Mg, Mg82Zn18 (at.%), Mg64Zn36 (at.%), and pure Zn in 3.5% NaCl solution. Mg64Zn36 had (i) an amorphous microstructure with some nano-scale grains, (ii) a corrosion rate substantially lower than that of pure Mg, and (iii) no hydrogen evolution during corrosion or anodic dissolution, because the positive corrosion potential retarded the cathodic hydrogen evolution. This is a new route to prevent hydrogen evolution during Mg corrosion, which has never previously been realized.

Magnetic property applications of microwave method prepared zinc ion modified CoAl2O4 nanoparticles

Employing Microwave combustion technique and utilizing L-arginine as fuel pure Cobalt Aluminate and Zn doped Cobalt Aluminate nanoparticles (NPs) were prepared. XRD, DRS-UV, HRSEM and VSM techniques were used to investigate the structural, optical, morphological, and magnetic properties. The average crystallite size is found in the range of 15 - 24 nm. Elemental confirmation is done by aid of EDX spectra. The band gap values of the produced samples were discovered to be between 2.57 and 2.45 eV. At room temperature, the prepared samples showed diamagnetic magnetic characteristics, which were corroborated by Magnetization–Field (MH) hysteresis curves.

Sn Alloying to Inhibit Hydrogen Evolution of Zn Metal Anode in Rechargeable Aqueous Batteries

AbstractThe detrimental hydrogen evolution side reaction is one of the major issues hindering the commercialization of Zn metal anode in high‐safety and low‐cost rechargeable aqueous batteries. Herein, the authors present a Sn alloying approach to effectively inhibit the hydrogen evolution and dendrite growth of the Zn metal anode. Through in situ monitoring of the hydrogen production during repeated plating/stripping tests, it is quantitatively demonstrated that the hydrogen evolution of alloy electrode with appropriate Sn amount is only half of that of pure Zn electrode. Furthermore, the Sn alloying allows for favorable Zn nucleation sites, lowering the Zn nucleation energy barrier and promoting more uniform Zn deposition. The Zn‐Sn alloy electrode offers much‐improved plating/stripping cycling, that is, over 240 h at 5 mA cm−2 and 35.2% depth of discharge. This work provides a practically viable strategy to stabilize Zn metal electrode in rechargeable aqueous batteries.

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.

Corrosion Behavior of Zn, Fe and Fe-Zn Powder Materials Prepared via Uniaxial Compression.

Powder metallurgy is one of the most prevalent ways for metallic degradable materials preparation. Knowledge of the properties of initial powders used during this procedure is therefore of great importance. Two different metals, iron and zinc, were selected and studied in this paper due to their promising properties in the field of biodegradable implants. Raw powders were studied using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDX). Powders (Fe, Zn and Fe-Zn in a weight ratio of 1:1) were then compressed at the pressure of 545 MPa to the form of pellets with a diameter of 1.7 cm. Surface morphology and degradation behavior in the Hanks´ solution were studied and evaluated. Electrochemical polarization tests along with the static immersion tests carried out for 21 days were employed for corrosion behavior characterization. The highest corrosion rate was observed for pure Zn powder followed by the Fe-Zn and Fe, respectively. A mixed Fe-Zn sample showed similar properties as pure zinc with no signs of iron degradation after 21 days due to the effect of galvanic protection secured by the zinc acting as a sacrificial anode.