Characterization of ZnO-Doped Hydroxyapatite Coatings on PEEK Made by Hybrid Plasma Spraying Process for Biomedical Applications

Due to its similar Young’s modulus to bone, polyetheretherketone (PEEK) shows potential as an alternative to metallic implants, avoiding the stress-shielding effect. Hydroxyapatite (HAp) coatings promote bone growth on the implant surface, while zinc oxide acts as an antibacterial agent. This study aims to develop functional coatings on PEEK that simultaneously stimulate bone growth and exhibit antibacterial properties. ZnO-doped HAp coatings were applied to PEEK using a powder mixture of ZnO/HAp and hybrid process (atmospheric plasma spraying and solution precursor plasma spraying). With powder mixtures, the ZnO content in the coatings could be determined without phase change, with nearly half of the initial ZnO powder lost. Meanwhile, using hybrid methods, the aerosol precursor zinc nitrate couldn’t fully convert into zinc oxide, resulting in the presence of intermediate zinc hydroxynitrate (up to 39.38%) in the as-sprayed coatings. Subsequently, the zinc hydroxynitrate could be converted to zinc oxide after heat treatment.