Page 46 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

CHAPTER 3
Abstract
Due its good properties, Magnesium (Mg) is a metal widely used in industrial applications and in biomedical field. However Mg is highly reactive and its wear and corrosion resistance are low. Plasma electrolytic oxidation (PEO), also known as microarc oxidation (MAO), is a favorable technique which can be used to produce coatings of MgO/ Mg(OH)2 in a controlled way with specific morphology, thickness and composition by the modification of the opera- tion parameters of the system such as voltage, current density, time and electrolytic solution. The aim of this paper was to study the effect of some additives in the base electrolyte solution composed of silicate and potassium hydrox- ide. Sodium fluoride was chosen since this is a commonly used additive and it was compared with two unreported organics compounds, hexamethylenetetramine and mannitol. Anodic system was operated under galvanostatic and potentiostaic mode. Curves voltage-time and current density-time were obtained and analyzed. After that, those results were correlated with SEM images of the surfaces and cross-sections in order to know the effect of these changes on the thickness and morphology of the coatings. Finally it was possible to conclude that coatings obtained by addition of sodium fluoride were compact and for hexamethylenetetramine and mannitol the coatings consisted of interconnected pores. Additionally it was observed that with an increment in the current or voltage applied to the system, increment in both the thickness and porous sizes were obtained.
Key words: Anodizing, magnesium, hexamethylenetetramine, mannitol, sodium fluoride, galvanostatic, potentio- static, silicate
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