Synthesis and characterization of Ti(IV)-substituted calcium hydroxyapatite particles by forced hydrolysis of Ca(OH)2-Na5P3O10-TiCl4 mixed solution

Ti(IV)-substituted calcium hydroxyapatite (TiHap) particles were prepared by aging Ca(OH) 2 , TiCl 4 , and sodium triphosphate (sodium tripolyphosphate, Natpp: Na 5 P 3 O 10 ) mixed solution at 100 °C for 18 h. The ellipsoidal secondary TiHap particles with ca. 100∼150 nm in length composing by aggregation of small ellipsoidal primary particles with ca. 20 nm in length were produced at atomic ratio of Ti/(Ca+Ti) [X Ti ]≦0.2. The in situ IR spectra of these TiHap particles exhibited very small bulk OH − band at 3,570 cm −1 . This result indicated that the TiHap particles were formed by aggregation of fine primary particles and OH − ions along with c -axis in the primary particles were disordered. The TiHap particles with Ca/P atomic ratio larger than theoretical value of 1.67 did not exhibit surface P–OH groups at 3,659 and 3,682 cm −1 . The diffuse reflectance UV spectra of TiHap particles revealed that these particles have a UV absorption property, especially fabricated at X Ti = 0.1. The particles prepared at X Ti = 0.6 and 0.8 were amorphous and nanoparticles with 5∼10 nm in diameter, but those precipitated at X Ti = 1.0 were poorly crystallized anataze-type TiO 2 nanoparticles.