Guar gum-driven high-energy plasma electrolytic oxidation for concurrent improvements in the electrochemical and catalytic properties of Ti-15 Zr alloy
“…This microstructure arises from the electron avalanche phenomenon triggered by electrical micro-discharges within the oxide layer. When a substantial electron current passes through the discharge channel, adjacent oxide materials undergo melting due to the pressure exerted by the emitted gases [ 17 ]. Fig.…”
“…This microstructure arises from the electron avalanche phenomenon triggered by electrical micro-discharges within the oxide layer. When a substantial electron current passes through the discharge channel, adjacent oxide materials undergo melting due to the pressure exerted by the emitted gases [ 17 ]. Fig.…”
“…41 The morphology and composition of the coating can be controlled by adjusting the parameters of the electrochemical deposition, and this technique allows complex 3D surfaces to be coated. 42,43 Two different compositional electrolytes were used in this study. One employs phosphate and fluoride (PF) salts and the other phosphate, fluoride, and silicate (PFS) salts.…”
Section: Discussionmentioning
confidence: 99%
“…This technique can also produce coatings containing calcium and phosphate that are biocompatible and that may be bioactive . The morphology and composition of the coating can be controlled by adjusting the parameters of the electrochemical deposition, and this technique allows complex 3D surfaces to be coated. , …”
Section: Discussionmentioning
confidence: 99%
“… 41 The morphology and composition of the coating can be controlled by adjusting the parameters of the electrochemical deposition, and this technique allows complex 3D surfaces to be coated. 42 , 43 …”
Resorbable Mg and Mg alloys have gained significant interest as promising biomedical materials. However, corrosion of these alloys can lead to premature reduction in their mechanical properties, and therefore their corrosion rate needs to be controlled. The aim of this study is to select an appropriate environment where the effects of coatings on the corrosion rate of the underlying Mg alloy can be discerned and measured in a relatively short time period. The corrosion resistance of uncoated AZ31 alloy in different solutions [Hank's Balanced Salt Solution, 1× phosphate buffered solution (PBS), 4× PBS, 0.9%, 3.5%, and 5 M sodium chloride (NaCl)] was determined by measuring the weight loss over a 2 week period. Upon exposure to physiological solutions, the uncoated AZ31 alloys exhibited a variable weight increase of 0.4 ± 0.4%. 3.5% and 5 M NaCl solutions led to 0.27 and 9.7 mm/year corrosion rates, respectively, where the compositions of corrosion products from AZ31 in all saline solutions were similar. However, the corrosion of the AZ31 alloy when coated by electrochemical oxidation with two phosphate coatings, one containing fluorine (PF) and another containing both fluorine and silica (PFS), showed 0.3 and 0.25 mm/year corrosion rates, respectively. This is more than 30 times lower than that of the uncoated alloy (7.8 mm/year), making them promising candidates for corrosion protection in severe corrosive environments. Cross-sections of the samples showed that the coatings protected the alloy from corrosion by preventing access of saline to the alloy surface, and this was further reinforced by corrosion products from both the alloy and the coatings forming an additional barrier. The information in this paper provides a methodology for evaluating the effects of coatings on the rate of corrosion of magnesium alloys.
“…Coatings fabricated via MAO have attracted much attention [ 1 , 26 , 27 , 28 ]. The most significant advantage of MAO coatings for use in biomaterials is the presence of pores on the coating surface and the ability to control the pore size by refining the process parameters [ 29 , 30 ].…”
A promising method for improving the functional properties of calcium-phosphate coatings is the incorporation of various antibacterial additives into their structure. The microbial contamination of a superficial wound is inevitable, even if the rules of asepsis and antisepsis are optimally applied. One of the main problems is that bacteria often become resistant to antibiotics over time. However, this does not apply to certain elements, chemical compounds and drugs with antimicrobial properties. In this study, the fabrication and properties of zinc-containing calcium-phosphate coatings that were formed via micro-arc oxidation from three different electrolyte solutions are investigated. The first electrolyte is based on calcium oxide, the second on hydroxyapatite and the third on calcium acetate. By adding zinc oxide to the three electrolyte solutions, antibacterial properties of the coatings are achieved. Although the same amount of zinc oxide has been added to each electrolyte solution, the zinc concentration in the coatings obtained vary greatly. Furthermore, this study investigates the morphology, structure and chemical composition of the coatings. The antibacterial properties of the zinc-containing coatings were tested toward three strains of bacteria—Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. Coatings of calcium acetate and zinc oxide contained the highest amount of zinc and displayed the highest zinc release. Moreover, coatings containing hydroxyapatite and zinc oxide show the highest antibacterial activity toward Pseudomonas aeruginosa, and coatings containing calcium acetate and zinc oxide show the highest antibacterial activities toward Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.
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