Focused ion beam sectioning studies of biomimetic hydroxyapatite coatings on Ti-6Al-4V substrates

Biomimetic hydroxyapatite (HA) coating has been used to render titanium implants with excellent osteoconductivity and osseointegration in orthopedic and dental applications. However, to date it has not been possible to reveal the fine details of the coating structure or the coating/substrate interface. In this study, a crack-free biomimetic HA coating has been successfully formed on sand-blasted, acid-etched Ti-6Al-4V discs by simply immersing the discs in a modified simulated body fluid (m-SBF). Dual-beam FIB/SEMs with either gallium ion source (GFIB) or xenon plasma ion source (PFIB) were used to prepare the cross-sections and thin transmission electron microscopy (TEM) specimens of the coating, and the capabilities of GFIB and PFIB were compared. Both the cross-sectional SEM and TEM images confirmed that a well bonded biomimetic HA coating has been formed on the Ti-6Al-4V substrate. The coating exhibits a gradient structure with a dense microstructure adjacent to the titanium substrate to facilitate strong bonding, while there is a porous structure at the surface, which is beneficial to bone cell attachment and subsequent new bone integration. [Display omitted] •A crack-free biomimetic HA coating has been formed on Ti-6Al-4V substrate.•GFIB and PFIB are compared to study the microstructure of the coating.•GFIB produces a cross-section with better quality, however, PFIB is more efficient.•The well bonded coating demonstrates a unique gradient structure.