Transformation of tricalcium phosphate into apatite by ammonia treatment?

Tricalcium phosphate, Ca-3(PO4)(2), was treated in dry ammonia at temperatu res between 1100 degreesC and 1300 degreesC for different times of up to 16 h. X-Ray diffraction and (3)1P-NMR studies showed a phase transformation i nto apatite when treated at temperatures between 1100 and 1200 degreesC. Ni trogen was detected in the treated samples with a maximum content of 2.9 wt %. (3)1P-NMR-analysis indicated no direct bonding of nitrogen to phosphorou s. The presence of graphite during ammonia treatment was required for nitro gen incorporation. Infrared spectra showed increasing intensities of four n ew bands at 3250, 2016, 1966 and 700 cm(-)1 attributed to the occurrence of cyanamide ions. Taking into account the results of XRD, (3)1P-NMR and FTIR spectrometry, it is concluded that tricalcium phosphate transforms into ca lcium deficient cyanamidapatite by ammonia treatments according to the reac tion: 3Ca(3)(PO4)(2) + H2CN2 --> Ca-9(PO4)(5)(HPO4)(HCN2). (C) 2001 Kluwer Academic Publishers.