Abstract
This study examined in detail the effect of the sintering process on hydroxyapatite (HAp) particles. The electron spin resonance (ESR) signal intensity of Mn2+ was measured and were made scanning electron microscopy (SEM) observations after the partial dissolution of HAp particles by lacttic acid.
The ESR signal intensity of Mn2+ decreased rapidly as the HAp particles fired at low temperature were dissolved with lactic acid solution, but that of the HAp fired at high temperature decreased only slightly. From these results, it was clear that the thermal reaction by firing at a low temperature took place only in the surface layer, and proceeded uniformly into the inner layer of the particles as the firing temperature increased. SEM observation of HAp particles before and after dissolution showed that the dentification of HAp particles occurred only from the surface layer and/or interface particles at lower firing temperature.
The sintering mechanism of HAp can be shown in a schematic representation, and is similar to the sintering theory of ceramics. ESR measurement is also applicable to elucidating the sintering mechanism of other ceramics as well as HAp.
