Micro-structural Characteristics and In-vitro Behaviour of Solution Precursor Plasma Sprayed Nanostructured Bioceramic Coatings

Hydroxyapatite (HA) is one of the most important bioceramics due to its excellent bioactivity. It is widely used as a bioactive coating to orthopedic implants to accelerate the osseointegration process. HA structure is flexible and can accommodate different ions like zinc (Zn) which is essential due to its role in many biological functions and is known to have antibacterial characteristic. Plasma spraying of HA powder is the commonly used deposition method, but an emerging process called solution precursor plasma spraying (SPPS) is an interesting one as it avoids powder preparation process and allows for the deposition of nanostructured coatings.

This current contribution presents the investigation of the micro-structural characteristics and the in-vitro behavior of SPPS HA and Zn-doped HA coatings. The coatings’ deposits were found to have unique microstructural features. XRD analysis showed that Zn concentration greater than 10 mol% inhibits HA formation. Rietveld refinement revealed that the unit cell parameters were not changed upon Zn addition suggesting that Zn ions did not substitute calcium but were likely inserted at the hydroxyl column. Moreover, the surface of the HA coatings was modified after in-vitro test due to the formation of apatite layer. The layer exhibited needle-like nanostructures observed through TEM.