Improved thermal and mechanical properties in hydroxyapatite–titanium composites by incorporating silica-coated titanium

• We successfully synthesized silica-coated titanium particles (STPs).
• STPs reduced the intensity of hydroxyapatite (HA) decomposition in HA–Ti composites.
• STPs prohibited the formation of CaTiO3 and TixPy phases in the composite.
• The calcium phosphate phases remained stable during the sintering process.

Hydroxyapatite–titanium composites are promising materials for fabrication of the load-bearing implants. However, the mechanical properties of these composites are negatively affected by formation of fragile compounds during the high-temperature processing. In this study, titanium particles were coated with a silica layer to decrease the metallic–ceramic interactions at the sintering temperature range. The results indicated the decomposition of hydroxyapatite and oxidation of titanium during the sintering process at 1100 °C. However, the undesired interactions between hydroxyapatite and titanium components were minimized, causing complete removal of calcium titanate and titanium phosphides as well as the formation of stable calcium phosphates in the sintered composite. Consequently, composites containing identical weight ratios of hydroxyapatite and silica-coated titanium exhibited a relatively high Vickers' hardness value comparable to that of titanium–hydroxyapatite composites with a weight ratio of 3:1. Therefore, surface modification of titanium particles using a silica layer could significantly improve the mechanical properties of the obtained composites by increasing their thermal stability during the sintering process.