Enhancement of the mechanical and biological properties of hydroxyapatite ceramics via a self-phase-nanoparticle additive approach

Normally, hydroxyapatite (HAp) ceramics exhibit several mechanical properties lower than the human bone. To enhance the mechanical properties, several improvement techniques have been proposed. In this work, we demonstrated an alternative approach to improve the mechanical performance of HAp ceramics by incorporating a self-phase nanoparticle additive. Specifically, micron-sized HAp ( m -HAp) derived from bovine bone was combined with nano-hydroxyapatite ( n -HAp), synthesized via a peroxide-based method. The resulting powder mixture was compacted into disk-shaped pellets using conventional uniaxial cold pressing and subsequently sintered at 1200 °C under atmospheric conditions. Effects of the n -HAp additive on the properties of the ceramics were investigated. All ceramic samples contained the main phase of HAp. However, the amount of β -tricalcium phosphate ( β -TCP) phase increased with the amount of n -HAp. The bulk density and mechanical properties of the ceramics improved, achieving optimal levels in samples containing 50 wt% n -HAp, while their grain size slightly increased. The observed improvements were linked to the nano-additive's significant promotion of surface diffusion during the sintering process. Bio-properties testing, including simulated body fluid (SBF), MTT assay, and protein adsorption tests demonstrated that the investigated HAp ceramic samples exhibited a desired bio-performance. Although the proposed technique could positively impact the properties of HAp ceramics, which are a type of biomaterial, it should also be improved to enhance the properties of other types of ceramics with various applications.