Abstract
The densification behavior of the green pellets with different densities prepared from hydroxyapatite powders consisting of plate-like particles was investigated. The green pellets were prepared by two methods, hydrothermal hot-pressing and uniaxial pressing, at different compression pressures. The hydrothermal hot-pressing gave the green pellets with densities higher than those using with uniaxial pressing. The shrinkage of the green pellets was observed by calcination at temperature above 800°C. The green pellets with higher bulk density gave the sintered compacts with higher density. When the calcination temperature was increased, densification proceeded with the increase in pore diameter and the decrease of pore volume. Even at temperature below 700°C, the size of pores increased with the increase in calcination temperature without shrinkage of the green pellets. Thus, the green compacts of the same density but with different pore sizes distribution prepared by hydrothermal hot-pressing and uniaxial pressing, had similar pore size distribution after calcination at 700°C, As a result, they had the same densification behavior by calcination at high temperature above 800°C. The densification behavior was found to be dependent on the density of green pellets, but not on the method of preparation of green pellets.
