Characterisation of TEOS-Based Sol–Gel-Hydroxyapatite Composite Coating on Titanium Implants

There is an urgent need for medical implant technologies with improved surface characteristics to ensure better fixation of metal implants without any adverse effect on the human body. The tetraethyl orthosilicate (TEOS) processed sol–gel silicates and hydroxyapatite (HAp) are known for their biocompatibility. In this study, we report sol–gel (TEOS)-hydroxyapatite (HAp) composites with improved film coatings on titanium alloy (Ti6Al4V) implants. The composites were synthesised at different molar ratios of TEOS: H2O (R) = 4, 16, and 32 at room temperature and dried at 70 °C compared to the high temperature (600–1200 °C) required for HAp-based composite preparation. Various characterisation studies were performed to determine its suitability for coating titanium (Ti) implants. Various surface treatments were performed on Ti substrates to enhance adhesion strength before coating. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) results confirmed the incorporation of HAp into the sol–gel and semi-crystalline nature of the sol–gel-HAp composite. Scanning electron microscope (SEM) revealed excellent fine particles forming flake-shaped agglomerates, whereas transmission electron microscopy (TEM) results depicted the size of grains ranging between 10 and 100 nm for R = 4, 16 and 32. The study found that the sol–gel-HAp composite prepared at R = 32 had a size distribution of 60–70 nm and demonstrated superior adhesive properties and surface characteristics compared to the other two composites (R = 4 and 16). The findings indicate that coating Ti- based implants with the R = 32 sol–gel-HAp composite can significantly improve their surface characteristics.