Physico-chemical and thermochemical studies of the hydrolytic conversion of amorphous tricalcium phosphate into apatite

Saida Somrani (1) , Mihai Banu (2) , Mohamed Jemal (3) , Christian Rey (2)

1 IPEIT - Institut Préparatoire aux Etudes d'Ingénieur de Tunis
2 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
3 FST - Faculté des Sciences Mathématiques, Physiques et Naturelles de Tunis

The conversion of amorphous tricalcium phosphate with different hydration ratio into apatite in water at 25 °C has been studied by microcalorimetry and several physical–chemical methods. The hydrolytic transformation was dominated by two strong xothermic events. A fast, relatively weak, wetting process and a very slow but strong heat release assigned to a slow internal rehydration and the crystallization of the amorphous phase into an apatite. The exothermic phenomenon related to the ehydration exceeded the crystalline transformation enthalpy. Rehydration occurred before the conversion of the amorphous phase into apatite and determined the advancement of the hydrolytic reaction. The apatitic phases formed evolved slightly with time after their formation. The crystallinity increased whereas the amount of HPO4 2− ion decreased. These data allow a better understanding of the behavior of biomaterials involving amorphous phases such as hydroxyapatite plasma-sprayed coatings.

Mots clés: Amorphous calcium phosphate; Apatite; Hydrolysis; Amorphous calcium phosphate; Crystallization -Microcalorimetry; Enthalpies

Domaines: Matériaux

Saida Somrani, Mihai Banu, Mohamed Jemal, Christian Rey. Physico-chemical and thermochemical studies of the hydrolytic conversion of amorphous tricalcium phosphate into apatite. Journal of Solid State Chemistry, 2005, 178 (5), pp.1337-1348. ⟨10.1016/j.jssc.2004.11.029⟩. ⟨hal-03601598⟩