Surface investigation of layered double hydroxides grown on the biodegradable AZ31 alloy

The magnesium AZ31 alloy is one of the most studied biodegradable materials for biomedical applications. It exhibits excellent biocompatibility and osseointegration and has an elastic modulus comparable to that of human bone. Furthermore, magnesium is essential for the metabolism in many biological mechanisms, and the Mg2+ ions, which are produced from its degradation, are useful to promote healing and tissue growth. However, the AZ31 alloy has the drawback of quickly degrading in the presence of biological fluids. Corrosion leads to a reduction of the implant's mechanical properties, compromising its functionality. Unlike other surface treatments that provide only a barrier function, the layered double hydroxides (LDHs) also offer the opportunity to release drugs. This work investigated the growth of LDHs on the AZ31 alloy by using three different nutrient solutions with (i) Zn(NO3)2*6H2O, (ii) Mg(NO3)2*6H2O, and (iii) FeCl3. The treatments were carried out at 90 degrees C for 12 h. The chemical composition and structure of treated surfaces were examined by scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The results of these analyses are presented and discussed.