Synthesis and characterisation of nanostructured hardystonite coating on stainless steel for biomedical application

Here, nanostructured hardystonite bioceramic (Ca₂ZnSi₂O₇) was synthesised from tetraethyl orthosilicate, zinc nitrate hexahydrate, and calcium nitrate tetrahydrate via sol-gel method, dried at 60-120°C, and finally calcinated at 1300°C. X-ray diffraction (XRD) analysis confirmed the formation of hardystonite bioceramic. Afterwards, electrophoretic method was utilised to coat the hardystonite ceramic on 316L stainless steel (SS). Methanol solution was used as suspension solvent. The best deposition procedure was carried out by electrophoretic device in the voltage of 50 V for 5 min. XRD analysis was employed for phase characterisation and scanning electron microscopy was utilised for microstructural and morphological characterisations of the coatings. Chemical composition of the coating was evaluated by energy-dispersive X-ray spectroscopy. The hardystonite coating improved the corrosion resistance of the substrate, so the corrosion current density in the coated samples was less than the uncoated ones (nine times). In order to assess the bioactivity of the coating, simulated body fluid was used. The main results of the coated sample bioactivity demonstrated that the nanostructured hardystonite coating could amend the in vitro SS bioactivity. Therefore, SS coated with nanostructured hardystonite may be a promising candidate to be applied as bioactive hard tissue implants.