Conversion of Marine Structures to Calcium Phosphate Materials: Mechanisms of Conversion Using Two Different Phosphate Solutions
Résumé
Marine structure, coralline materials were converted to calcium phosphate using two
different phosphate solutions. The aim was to study the conversion mechanisms under acidic and
basic environment at moderate conditions of temperature. Crystal growth and morphology of
converted corals were characterized by XRD and SEM respectively. The results suggested that
under acidic conditions (H3PO4), dissolution and precipitation control and direct the crystal
formation and morphology in which transition from plate like to rod like hydroxyapatite structure
was favoured. Metastable phase such as monetite formed and transformed to HAp during reaction.
During the first hour of the dissolution a monetite and hydroxyapatite mixture precipitates and then
the full conversion to hydroxyapatite is observed. On the other hand, under basic conditions
(NH4)2HPO4, just diffusional surface conversion of the calcium carbonate structure of coralline
materials to hydroxyapatite and a very small amount of tri-calcium phosphate is observed. The
mechanism can be classified as the solid-state topotactic ion-exchange reaction mechanism.
Domaines
Matériaux
Origine : Fichiers produits par l'(les) auteur(s)
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