The thermal stability of AB-type carbonated calcium phosphate apatites prepared by precipitation from aqueous media was studied. The behavior of powders was investigated using temperature programmed XRD, infrared spectroscopy and thermogravimetry. In N2 atmosphere, two successive peaks of decarbonatation with maxima at about 700 and 950C occurred. This behavior is explained by different substitution modes for carbonates in the apatite. The decarbonatation peaks were shifted to higher temperature under CO2 (around 900 and 1150°C). The analysis of the thermal stability allowed further densification of carbonate apatite ceramics without important carbonate loss.
The procedures recommended in Publications 30 and 66 by ICRP for calculating radiation doses from inhaled or ingested radionuclides include classification of material on the basis of different parameters, among which transportability plays a major role, The allocation of transportable Classes or absorption Types should, whenever possible, be based on animal or human data. However, when such in vivo data are unavailable, it becomes appropriate to consider the use of other approaches, among which in vitro dissolution techniques are reasonable alternatives. This paper reviews and critically analyzes in vitro dissolution techniques that have been described historically and recommends methods shown to be useful in estimating the in vivo solubility of radioactive particles.
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