title: Apatitic calcium orthophosphates and related compounds for biomaterials preparation.
abstract: The authors show that to obtain well chemically defined apatitic bioceramics and to know the possible transformations of this material during sintering, it is necessary to prepare a good starting material. Moreover, they show that it is possible to prepare a new organic-inorganic phosphate compound. The precipitation of apatite in an aqueous medium at boiling temperature was studied using the methodology of experimental design. Independent variables were the volume of NH4OH in phosphate solution, the volume of NH4OH in calcium solution, and the time of precipitation; the response was the atomic Ca/P ratio of the obtained precipitate. A continuous variation of this ratio from 1.63 to 1.73 is observed. Implications of this result to the preparation of pure HA: Ca10(PO4)6(OH)2 is given. Moreover, when Ca/P greater than 1.67, HA reacts with Ca(OH)2 (after heating at 1000 degrees C in air for some days) to give rise to a single phase described as a modified HA (MHA), a Ca/P ratio of 1.75, an a value of 9.373 +/- 0.002 A, and a c value of 6.884 +/- 0.002 A. The reactivity (time versus temperature) of the MHA is described. If the precipitation of the calcium phosphate is realized at 37 degrees C in a water-ethanol medium in the presence of A2EP, a new apatite, chemically bonded to the organic molecule by pooling phosphate groups, is obtained.
authors: Laboratoire de Physico-Chimie des Solides, Ecole Nationale Supérieure de Chimie de Toulouse, France.
authors: G
authors: G
authors: Bonel
authors: J C
authors: JC
authors: Heughebaert
authors: M
authors: M
authors: Heughebaert
authors: J L
authors: JL
authors: Lacout
authors: A
authors: A
authors: Lebugle
mesh_terms: D064753:Ammonium Hydroxide; D001031:Apatites; D001672:Biocompatible Materials / Q000032:analysis / Q000138:chemical synthesis*; D002118:Calcium / Q000032:analysis; D017610:Calcium Compounds; D002126:Calcium Hydroxide; D002130:Calcium Phosphates / Q000032:analysis / Q000138:chemical synthesis*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006358:Hot Temperature; D006878:Hydroxides; D006882:Hydroxyapatites / Q000032:analysis / Q000138:chemical synthesis*; D008956:Models, Chemical; D009943:Organophosphorus Compounds; D010087:Oxides; D010710:Phosphates / Q000032:analysis; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D001672:Biocompatible Materials; D017610:Calcium Compounds; D002130:Calcium Phosphates; D006878:Hydroxides; D006882:Hydroxyapatites; D009943:Organophosphorus Compounds; D010087:Oxides; D010710:Phosphates; D064753:Ammonium Hydroxide; C016538:lime; D002126:Calcium Hydroxide; D002118:Calcium