PREPARATION AND CHARACTERIZATION OF SPHERICAL CALCIUM HYDROXYAPATITE

The preparation of spherical calcium phosphate particles by aging a so lution containing CaSO4 and NaH2PO4 at 80 and 100 degrees C in the pre sence of urea (1 mol/dm(3)) and a surfactant [cetyltrimethylammonium c hloride; CTAC] (1.0 x 10(-2) mol/dm(3)) has been investigated, and the ir properties were characterized by X-ray diffraction (XRD), Fourier t ransform infrared (FTIR), scanning and transmission electron microscop y (SEM and TEM), N-2 and H2O adsorption measurements, and thermogravim etric-differential thermal analyses (TG-DTA). The size and shape of th e particles produced strongly depended on the concentration of the rea ctants and the aging temperature. Spherical calcium hydroxyapatite par ticles were precipitated only within a narrow concentration domain of reactants after aging at 100 degrees C for 3 h. The spherical calcium hydroxyapatite particles produced at [CaSO4] = 2.0 x 10(-3) mol/dm(3) and [NaH2PO4] = 7.9 x 10(-4) mol/dm(3) were agglomerates of small plat elet particles and were B-type carbonate hydroxyapatite in which 4.8 w t % of CO32- ions are substituted for PO43- ions. The results of chemi cal analysis and TG identified the formula of the particles as Ca8.5Na 1.5(PO4)(5.4)(CO3)(0.8)(OH)(0.7).1.2H(2)O. The texture and crystallini ty of the spherical calcium hydroxyapatite particles were sustained up to 1000 degrees C, and the particles showed the selective adsorption of H2O molecules. This selective adsorption was more pronounced after calcining the samples in air.