Optical transmittance changes of solid preforms with temperature - I. Highpressure densified hydroxyapatite gels

The light transmittance-temperature patterns are recorded and partially int erpreted for thin pellets of hydroxyapatite gels consolidated by the cold i sostatic pressure (500 MPa and 1000 MPa). In the course of processing the p recipitated wet gels were washed by methanol, ethanol, and propanol, prior to their drying and a subsequent high pressure consolidation. Three important processes taking place have been identified by means of the se patterns: the elementary carbon evolution and its subsequent oxidation a t temperatures around 600 degrees C, the shrinkage of samples in the temper ature interval between 700 degrees C and 1000 degrees C, and also a bloatin g of samples at temperatures above 1000 degrees C.