فصلنامه علوم و مهندسی سطح ایران
پیاپی 49 (پاییز 1400)

The use of an environmentally friendly method called plasma electrolytic oxidation (PEO) on aluminum and its alloys to create a coating with desirable properties is very important. One of the parameters affecting of PEO process as well as the performance of the prepared coatings is the composition of the substrate. In this study, the effect of increasing the percentage silicon of substrate on the plasma electrolytic oxidation process with bipolar pulse current in a silicate-based electrolytic bath was investigated. The results showed that at constant current, the rate of increase of positive voltage decreases with increasing the amount of silicon and the values of positive voltage approach each other with the onset of oxidation. Scanning electron microscopy was used to evaluate the morphology and structure of the coating and X-ray diffraction test was used for phase detection. With increasing the percentage silicon of substrate from 1 to 13% by weight, in addition to reducing the thickness and roughness of the coatings, the average coating speed also decreased from 1 to 0.43μm / min. As the Si content of the substrate increases, volcano-shaped morphology dominated over pancake morphology in the growth of the coating and a porous surface with scattered micro-pores in its structure was observed. The results showed coatings mainly containing mixtures of γ-Al2O3, η-Al2O3, δ-Al2O3, SiO2 and a small amount of mullite and some amorphous phases.

Bioactivity and antibacterial properties have been recognized as important factors which can result in the success of titanium- based replacements in the orthopedic surgeries. In the present study, silver nanoparticles (nAg) and HP particles (containing the same ratio of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP)) were coated on titanium substrate through using sol-gel method to induce both bioactivity and antibacterial properties. The prepared composite coating then was characterized via scanning electron microscopy (SEM ) equipped with X-ray diffraction (EDX), bioactivity assessment, anti-bacterial evaluation, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (M TT) test. The obtained results showed that HP/nAg coating on titanium substrate enhanced bioactivity, anti-bacterial performance, and cell viability comparable with pure titanium. The overall results indicated that the coated substrate containing HP (β-TCP/HA = 50:50) with 2% nA g on Ti plates can be a reliable candidate for further studies.

mproving corrosion resistance is one of the main goals of orthopedic implants. In this regard, this study aims to improve the quality and efficiency of the AZ31 M agnesium alloy by phosphate coatings containing hydroxyapatite and ZnO nanoparticles by M AO method. For this purpose, first, the effect of adding hydroxyapatite nanoparticles in constant current mode was investigated and then the effective parameters in this method, including time and duty cycle, were studied. Corrosion behavior of the coatings was investigated in Ringer's solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). M icrostructural and phase studies of coatings by field emission scanning electron microscopy (FESEM /EDS) and X-ray diffraction (XRD) analysis before and after corrosion test showed better performance of the coating produced in the electrolyte containing 3 grams per liter of hydroxyapatite nanoparticles in 7 minutes and 50% duty cycle.