title: Influence of synthesis and sintering parameters on the characteristics of carbonate apatite.
abstract: A new method to synthesise carbonate-substituted hydroxyapatite (CHA) powder has been set up introducing a CO(2) flux, as a source of carbonate, in the HA synthesis process based on the neutralisation reaction. The reactants are abundant and inexpensive. The yield is good compared to other CHA powder synthesis. The reaction may be performed at low temperature and without pH control and does not produce any by-products. The influence of the synthesis parameters (temperature, H(3)PO(4) solution dropping rate, i.e. reaction time, CO(2) flux, ageing time) has been tested to optimise the process conditions in order to obtain the highest carbonation degree and favour the B-type CHA precipitation with respect to A-type one. The prepared powder (5.8wt% of total carbonate with an A/B ratio of 0.78) was thermally treated at various temperatures in the range 500-1400 degrees C in different atmospheres (air, wet and dry carbon dioxide). The thermal treatments were performed with a double aim, to eliminate selectively the carbonate groups in A-position maintaining the B-type substitution, and to evaluate the thermal stability of the CHA and the total loss of carbonate as a function of temperature. The thermal treatment at 900 degrees C in wet CO(2) gave the best result in terms of a high carbonate residue and a low A/B ratio. We also investigate the use of different techniques (inductively coupled plasma, TGA, Fourier transformed infrared spectroscopy, X-ray diffraction) for characterising CHA and calculating sensitivity and accuracy in the quantification of carbonate ions for each molecular site.
authors.affiliation: Institute of Science and Technology for Ceramics ISTEC-CNR, via Granarolo 64, 48018 (RA), Faenza, Italy. elena@istec.cnr.it
authors.forename: Elena
authors.initials: E
authors.lastname: Landi
authors.forename: Anna
authors.initials: A
authors.lastname: Tampieri
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Celotti
authors.forename: Lucia
authors.initials: L
authors.lastname: Vichi
authors.forename: Monica
authors.initials: M
authors.lastname: Sandri
mesh_terms: D001031:Apatites / Q000737:chemistry* / Q000302:isolation & purification / Q000528:radiation effects; D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D006358:Hot Temperature; D008422:Materials Testing / Q000379:methods*; D008968:Molecular Conformation; D010316:Particle Size; D010756:Phosphoric Acids / Q000737:chemistry; D011208:Powders; D013499:Surface Properties
chemical_list: D001031:Apatites; D001672:Biocompatible Materials; D010756:Phosphoric Acids; D011208:Powders; D002245:Carbon Dioxide; C030782:carboapatite