Features of the Kinetics of Sintering of Hydroxyapatite Powders with Various Particle Sizes

Abstract

The kinetics of sintering of nanosized (20 nm) and microsized (0.7–0.9 μm) hydroxyapatite (HA) powders with continuously increasing temperature at a constant rate was studied by dilatometry. The sintering of the HA micropowders within the temperature range 1100–1300°C occurred by the mechanism of diffusion-viscous flow of crystalline particles. The kinetics of the process was described by a power-law function of time; i.e., the process rate depended on current shrinkage. The shrinkage of the nanopowders within the sintering temperature range was directly proportional to temperature, occurred by the law of viscous flow of amorphous particles, and was independent of the temperature increase rate. The apparent sintering activation energies of the studied micro- and nanopowders were 180 and 60 kJ/mol, respectively.