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Zinc based materials have been studied as candidates for the fabrication of biodegradable implants. For applications in orthopedics, porous materials with reduced modulus of elasticity are desirable. Fabrication of porous zinc is challenging due to several processing difficulties, such as low melting point, easy evaporation and high reactivity with many porogen agents. In this work, we prepared a porous zinc sheet by thermal plasma spraying with a porosity of 16.8%. Mechanical, corrosion and biological characteristics of the prepared material were studied in detail. The porous zinc possessed reduced moduli of elasticity (2-6 GPa) and relatively high values of strengths (12-55 MPa—depending on the loading mode). The corrosion rate of the porous zinc was approximately 0.1 mm/a, and the extracts showed excellent murine L929 cell viability. The results suggest that thermal plasma spraying is usable for preparation of biodegradable porous zinc scaffolds. [ABSTRACT FROM AUTHOR]

Recently, zinc-based materials have been extensively investigated as materials suitable for the fabrication of biodegradable orthopedic implants. In this study, porous zinc was prepared as a material for implantation into trabecular bone using spark plasma sintering with different sizes of initial zinc powders, and microstructural, mechanical and corrosion characterizations of the prepared materials were performed. The porosity of the prepared porous samples was approximately 20%. The mechanical properties depended on the initial powder particle size, the pore size and distribution. By using a finer powder (FP), <100 μm in size, the compressive yield strength and the compressive modulus were approximately 31.2 MPa and 1.2 GPa, respectively. These values approach those of trabecular bone (1–12 MPa and 0.1–0.4 GPa). Moreover, the plastic deformation of FP materials occurred at almost constant stress similar to trabecular bone. The corrosion rates of the porous Zn were 0.6–0.8 mm/a and depended on the initial powder particle size, the pore size and distribution. After pre-incubation of the porous Zn in simulated body fluid (SBF), the Zn concentration in biological extracts was below the toxic limit of zinc for L929 cells. Based on the obtained results, we can estimate that the materials prepared from the finer zinc powder showed properties suitable for the fabrication of porous biodegradable orthopedic implants. [ABSTRACT FROM AUTHOR]

Research on biodegradable iron-based materials has been increasing because they appear suitable for fabrication of temporary orthopedic and cardiovascular implants. Preliminary in vitro and in vivo studies have found that iron and some of its alloys exhibit good cyto- and biocompatibility. The main disadvantage of pure iron is its insufficient corrosion rate in physiological environments; therefore, it is necessary to modify it by suitable alloying. In this study, iron alloys containing 2 wt % of palladium, silver or carbon were prepared using powder metallurgy. The microstructure, mechanical and corrosion properties in a simulated body fluid were characterized. Compared to pure iron, alloying slightly increased porosity (from 15% to ∼ 18%) and decreased the compressive modulus of elasticity (from 5.6 to 1.1–1.8 GPa), compressive proof strength (from 145 to 113–127 MPa) and the Vickers hardness (from 63 to 23–37). Alloying with palladium and carbon enhanced (whereas silver lowered) the corrosion rate of iron in a simulated body fluid. Based on the obtained results, carbon and especially palladium appear to be suitable alloying elements for iron-based biodegradable materials. [ABSTRACT FROM AUTHOR]

Research into biodegradable porous materials has been increasingly focused on iron-based materials because such materials possess suitable properties for orthopedic applications. In this study, we prepared porous iron with porosities of 32-82 vol.% by powder metallurgy using ammonium bicarbonate as a space-holder material. We studied the influence of initial powder size and compacting pressure on sample microstructure, contamination and mechanical characteristics. The experimental results were analyzed as well, using Gibson-Ashby model and this analysis showed a good agreement in theoretical and experimental data. Whereas increasing compression pressure decreased porosity, the use of finer iron powder led to an increase in porosity. Increasing the amount of space-holder material in the initial mixture increased the total porosity, improved compressibility and consequently decreased the number of pores originating from imperfect compaction. A higher compacting pressure and the use of finer powder enhanced both the flexural and compressive properties. Even the most porous samples prepared from the fine iron powder possessed mechanical properties comparable to human cancellous bone. Based on these results, we can claim that the use of fine initial iron powder is necessary to obtain highly porous iron, which appears to be suitable for orthopedic applications. [ABSTRACT FROM AUTHOR]

The demand for porous biodegradable load-bearing implants has been increasing recently. Based on investigations of biodegradable stents, porous iron may be a suitable material for such applications. In this study, we prepared porous iron samples with porosities of 34–51 vol.% by powder metallurgy using ammonium bicarbonate as a space-holder material. We studied sample microstructure (SEM-EDX and XRD), flexural and compressive behaviors (universal loading machine) and hardness HV5 (hardness tester) of the prepared samples. Sample porosity increased with the amount of spacer in the initial mixtures. Only the pore surfaces had insignificant oxidation and no other contamination was observed. Increasing porosity decreased the mechanical properties of the samples; although, the properties were still comparable with human bone and higher than those of porous non-metallic biomaterials and porous magnesium prepared in a similar way. Based on these results, powder metallurgy appears to be a suitable method for the preparation of porous iron for orthopedic applications. [ABSTRACT FROM AUTHOR]

In this study, we prepared zinc wires with a diameter of 250 µm by direct extrusion using an extrusion ratio of 576. We studied the influence of the extrusion temperature and microstructure of the initial Zn billets on the microstructural and mechanical characteristics of the extruded wires. The extrusion temperature played a significant role in the final grain size. The wires extruded at 300 °C possessed a coarse-grained microstructure and the shape of their tensile stress–strain curves suggested that twinning played an important role during their deformation. A significant influence of the initial grain size on the final microstructure was observed after the extrusion at 100 °C. The wires prepared from the billet with a very coarse-grained microstructure possessed a bimodal grain size. A significant coarsening of their microstructure was observed after the tensile test. The wires prepared from the medium-grained billets at 100 °C were relatively coarse-grained, but their grain size was stable during the straining, resulting in the highest ultimate tensile strength. This preliminary study shows that strong attention should be paid to the extrusion parameters and the microstructure of the initial billets, because they significantly influence the microstructure and mechanical behavior of the obtained wires. [ABSTRACT FROM AUTHOR]

Zinc and its alloys seem to be promising candidates for biodegradable applications. Those materials are often modified by other elements or compounds in order to enhance their properties. The combination of zinc and apatites is challenging for several reasons. However, the advantages connected with the biological aspects suggest the need for further research into such materials. In this study, three zinc-based composites with 4 and 8 wt. % of nanohydroxyapatite or nanomonetite (Zn-4MO, Zn-4HA, Zn-8HA) were prepared by sintering and subsequent extrusion. Materials prepared in this way were characterized from the microstructural, mechanical and corrosion point of view. The obtained results showed a significant influence of particle character (amount and morphology) on the strength and ductility of the prepared materials. In case of Zn-4MO, the presence of monetite significantly increased the ductility compared with the other materials. In addition, the increment of the degradation rate caused by the presence of monetite was observed as well. All obtained results pointed out to significant advantages of monetite for the preparation of Zn-apatite composites compared with hydroxyapatite. [ABSTRACT FROM AUTHOR]

The Zn-based alloys, alloyed with the elements of the 2nd group of the periodic table, are considered as potential biodegradable materials suitable for the fabrication of small orthopaedic implants or cardiovascular stents. Unfortunately, the as-cast Zn-based alloys do not fulfil the requirements for mechanical properties for such applications. Extrusion is a thermomechanical process which is very powerful for breaking the cast microstructure and enhancing mechanical characteristics of metallic materials. In this study, we focused on the influence of extrusion parameters, such as temperature and extrusion ratio, on microstructural and mechanical characteristics of a ZnMg0.8Ca0.2 (wt.%) alloy. The extrusion led to a significant grain refinement and the formation of a crystallographic texture. Extrusion temperature played a more significant role in the mean grain size compared to the extrusion ratio (ER). At lower extrusion temperatures, the texture was less intensive and the subsequent mechanical anisotropy was weaker. Constants for the prediction of the grain size based on the Zener-Hollomon parameter were obtained. Prediction of mechanical properties using the Hall-Petch relationship appeared to be difficult because of the dependence of the texture on the extrusion temperature. Extrusion at the temperatures of 200 °C (ER = 25:1) and 150 °C (ER = 11:1) led to mechanical performance fulfilling the requirements for implantology. [ABSTRACT FROM AUTHOR]

Zinc and its alloys belong to a group of biodegradable materials, which can be potentially used for the preparation of temporary orthopedic implants. The research of biodegradable zinc materials revealed a lot of limitations; however, the new processing approaches of those materials can enhance their properties, which are insufficient for now. In this study, the zinc composite with 8 wt.% of hydroxyapatite (Zn/HA8) prepared for the first time by extrusion process was characterized from the point of view of the structural, mechanical and corrosion properties. The extrusion process led to good integrity of the interfaces between the zinc and hydroxyapatite particles. Mechanical behavior confirmed the role of hydroxyapatite as a defect in the material structure, which led to a decrease of the Zn/HA8 mechanical properties by approximately 30% (compressive yield strength (CYS) = 154 MPa Zn, 113 MPa Zn/HA8). Despite that, the Zn/HA8 composite showed sufficient mechanical properties for cancellous bone replacement and reached the lower limit for cortical bone. Additionally, the presence of hydroxyapatite caused the preferential precipitation of hydroxyapatite (HA) from the solution and can lead to a significant enhancement of the tissue/implant interface interactions. [ABSTRACT FROM AUTHOR]

Zinc-based alloys containing the elements of the second group of the periodic table have been extensively studied as potential candidates for applications as a biodegradable material. In this study, the ZnMg0.8Ca0.2 (wt%) alloy was prepared and treated by annealing and extrusion at various conditions. The evolution of microstructure and mechanical properties during annealing and after extrusion was performed in detail. Both annealing and extrusion caused microstructural changes influencing mechanical properties. Annealing caused a homogenization of the microstructure and transformation of metastable phases. The extrusion caused a rearrangement of the intermetallic phases, a refinement and a texturing of the zinc matrix. Those lead to a significant strengthening and to an increase in the ductility, but also to mechanical anisotropy. In this paper, the influence of the processing on the microstructure and mechanical properties is discussed in detail based on the results obtained by various methods, such as scanning and transmission electron microscopy, electron backscattered diffraction, tensile and compressive mechanical testing and nanoindentation. • Solidification mechanism of a ZnMg0.8Ca0.2 (wt%) alloy was proposed. • Formation of Zn-MgZn 2 eutectics was observed. • Influence of annealing and extrusion was studied. • Anisotropy of the extruded alloy was explained. [ABSTRACT FROM AUTHOR]

Zinc and zinc alloys have been studied due to their corrosion properties as potentially biodegradable materials. In this study, a zinc/hydroxyapatite composite (Zn/HA) containing 16 wt % HA was prepared by spark plasma sintering and characterized in detail. The microstructure, mechanical and corrosion properties were studied and the mutual relations between properties and microstructure were found. The porosity was evaluated to be approximately 18%. The mechanical properties (ultimate compression strength = 65 MPa and ultimate flexural strength = 120 MPa) are sufficient for the potential scaffolding and augmentation of cancellous bone. The flexural properties of these materials were measured for the first time. Immersion tests and subsequent analyses confirmed no direct participation of hydroxyapatite in the corrosion process and an ideal corrosion rate of approximately 0.4 mm/year. The amount of released zinc was between 4–6 mg/day corresponding with the maximal usable surface area of 25 cm2. All the results suggest that the Zn/HA composite is suitable as a potential biodegradable material (from the point of view of mechanical and corrosion properties) for the replacement of cancellous bones. [ABSTRACT FROM AUTHOR]

Zinc-based alloys represent one of the most highly developed areas regarding biodegradable materials. Despite this, some general deficiencies such as cytotoxicity and poor mechanical properties (especially elongation), are not properly solved. In this work, a Zn-5Mg (5 wt.% Mg) composite material with tailored mechanical and superior corrosion properties is prepared by powder metallurgy techniques. Pure Zn and Mg are mixed and subsequently compacted by extrusion at 200 °C and an extrusion ratio of 10. The final product possesses appropriate mechanical properties (tensile yield strength = 148 MPa, ultimate tensile strength = 183 MPa, and elongation = 16%) and decreased by four times the release of Zn in the initial stage of degradation compared to pure Zn, which can highly decrease cytotoxicity effects and therefore positively affect the initial stage of the healing process. [ABSTRACT FROM AUTHOR]

The objective of this study is to comprehensively investigate the formation mechanism of hopeite on a promising biodegradable Zn-0.8Mg-0.2Sr alloy during its self-corrosion process and its subsequent influence on the interaction of the material with cells and bacteria. Notably, the self-corrosion process of Zn-based alloys inherently generates Zn2+ ions, eliminating the necessity for additional zinc compounds in the treatment. The investigation focused on the chemical composition of the applied baths, exposure time, and temperature, in order to analyze the structure, quality, distribution, phase composition, thickness, and roughness of the resulting layers bringing range of key pros and cons for suggested materials. While the thin layers are considered more beneficial in a wide range of applications, the resulting thinnest layer was observed after exposure to the bath containing additives at 50 °C for 24 h, measuring approximately 192 ± 21 pm in thickness. In addition, the layer possessed the most homogeneous distribution under these conditions. Generally, the layers formed in the bath without additives exhibited higher thickness and rougher surfaces compared to those in the bath containing additives. Such results had a direct impact on dissolution rate, cytotoxicity, and antibacterial properties. The highest dissolution rate (40.7 mg·cm−2·day−1) indicating a limited lifetime of the layer was obtained for material processed under the following coating condition: 50 °C, 24 h, and bath without additives. The general presence of surface layers manifested in increased cell viability under direct cytotoxicity test, while smoother surface conditions also supported the antibacterial properties, both making suggested treatments as interesting variations for biodegradable zinc-based materials. [Display omitted] • Layers formed in the bath without additives exhibit higher thickness. • Layers formed in the bath without additives exhibit rougher surfaces. • The presence of fluoride anions allows the formation of MgF 2 acting as protective against dissolution. • Surface layers manifest increase cell viability under direct cytotoxicity test. • Smoother surface supports antibacterial properties. [ABSTRACT FROM AUTHOR]

• Zn-0.8Mg-0.2Sr was successfully extruded in the temperature range 150–300 °C. • Materials extruded at 150 and 200 °C dominated by fine-grained microstructure. • Elongation increased with lower extrusion temperature and higher extrusion ratio. • Various deformation mechanisms dominated under different loading. Zinc-based alloys containing elements well-tolerated by the organism (Mg, Ca, Sr) are considered as perspective biodegradable materials for an application like medical devices such as fixations of fractured bones or even stents. In the presented paper we characterize the relations between microstructure and mechanical properties of extruded Zn-0.8Mg-0.2 Sr alloy (wt%) depending on various parameters like extrusion temperature (150–300 °C) and ratio (11 or 25). Typical analysis including SEM with EBSD and mechanical tests indicate a strong dependence of obtained data on both extrusion temperature and ratio. Relatively wide range of elongation to fracture (2–22%) and anisotropy in compression yield strengths regarding loading direction (50–150 MPa) are explained by the huge effect of grain size, material texture and also the existence of dislocation substructures in materials extruded at elevated temperatures. Based on obtained results, appropriate extrusion conditions (200 °C, extrusion ratio 25) are suggested to reach the combination of superior mechanical properties 244 MPa, 324 MPa and 22% for tensile yield strength, ultimate tensile strength and elongation to fracture, respectively. [ABSTRACT FROM AUTHOR]