Hydroxyapatite (HAp) with compositions of stoichiometric (Ca/P = 1.67) and nonstoichiometric (Ca/P<1.67) is of considerable interest as an excellent material for artificial bones and teeth, for chromatographic separation of bio- macromolecules and for gas sensors. Although HAp is used for artificial bones and teeth but its fracture toughness and static fatigue failure are not satisfactory. The difficulty in obtaining desired properties of HAp stems from the fact that their preparation are mostly done in bulk aqueous media in which uncontrolled nucleation and grain growth cannot be prevented. Synthesis of these compounds as nanoparticle in constrained microreactors such as the aqueous cores of water-in-oil microemulsion seems to be a promising alternative. We have proposed a method to optimize and control the size of HAp on nano-scal with narrow size distribution by a proper modulation of certain physico-chemical conditions of the microemulsion. These nanoparticles of HAp would be characterized by Ca/P ratio, X-ray diffraction, scanning electron microscope, and transmission electron microscope. We expect a higher density, higher strength, and microhomogeneous HAp ceramic for nanoparticle-derived samples. The measurements of mechanical properties of sintered nanoparticles of HAp would reveal the benefits of microemulsion processing.
Recently, we have developed crystalline nanoparticles of hydroxyapatite in Phase I. We have planned to use these particles in various biomedical applications in Phase II. We will mix nanocrystalline hydroxyapatite to the dental materials for increasing their tensile strength and fracture toughness. While in area of orthopedic, the coating of nanocrystalline hydroxyapatite on alloy implants will be carried out to increase their bioactivity. The reabsorbable screws and plates made from nanocrystalline hydroxyapatite for craniofacial surgical applications will improve their mechanical properties. The strength of implants developed from nanocrystalline hydroxyapatite and binding materials, such as PMMA, can be made equivalent to the strength of bone.
