title: Fibrous growth of tricalcium phosphate ceramics.
abstract: Structural transformation and sintering processes of tricalcium phosphate (TCP) ceramics prepared from defective hydroxyapatite (Ca9HPO4(PO4)5OH) were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). Starting powders with Ca/P ratio approximately 1.5 were obtained by adding 0.5 l of 0.3 M H3PO4 solution to an equal volume of 0.45 M Ca(OH)2. In the prepared ceramics, the onset temperature for transformation of defective hydroxyapatite into TCP (witlokite) agrees with the onset temperature for sintering (800 degrees C). Sintering occurs through the formation of a fibrous structure, which resembles biological hard tissue. In the 1000-1200 degrees C range, these fibres coalesce into grains of up to 0.6 microm in size with a fibrous-laminar morphology. At the end of this sintering stage witlokite transforms into alphaTCP. At about 1450 degrees C, partial decomposition of alphaTCP into Ca2P2O7+Ca4P2O9 is observed. AFM observations suggest that Ca2P2O7 is segregated in the liquid state and increases the velocity of grain growth (up to 12 microm).
authors.affiliation: ESFM, Instituto Politécnico Nacional. U.P. Adolfo López Matéos, Edif. 9 México D.F., 07738.
authors.forename: J J
authors.initials: JJ
authors.lastname: Prieto Valdés
authors.forename: J
authors.initials: J
authors.lastname: Ortiz López
authors.forename: G
authors.initials: G
authors.lastname: Rueda Morales
authors.forename: G
authors.initials: G
authors.lastname: Pacheco Malagon
authors.forename: V
authors.initials: V
authors.lastname: Prieto Gortcheva