Authors: Kaia Tõnsuaadu Kārlis Agris Gross Liene Plūduma Mihkel Veiderma
Publish Date: 2011/09/03
Volume: 110, Issue: 2, Pages: 647-659
Abstract
High temperature processing is essential for the preparation of apatites for biomaterials lighting waste removal and other applications This requires a good understanding of the thermal stability and transitions upon heating The most widely used is hydroxyapatite HAp but increasing interest is being directed to fluorapatite FAp and chlorapatite ClAp The structural modifications for substitutions are discussed to understand the temperature processing range for the different apatites This is based on a review of the literature from the past few decades together with recent research results Apatite thermal stability is mainly determined by the stoichiometry Ca/P ratio and structural substitutions and the gas composition during heating Thermal stability is lowered the most by a substitution of calcium and phosphate leading to loss in phase stability at temperatures less than 900 °C The anions in the hexagonal axis OH in HAp F in FAp and Cl in ClAp are the last to leave upon heating and prevention of the loss of these groups ensures high temperature stability The information discussed here will assist in understanding the changes of apatites during heating in calcination sintering hydrothermal processing plasma spraying flame pyrolysis and other hightemperature processesKT was supported by target financing by the MES of Estonia Project No SF0140082s08 and the Estonian Science Foundation Grants No 8207 KAG received support from the Marie Curie grant PIRG05GA2009249306 and jointly with LP from an ESF grant 2009/0199/1DP/11120/09/APIA/VIAA/090
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