Effect of sintering on porosity, phase, and surface morphology of spray dried hydroxyapatite microspheres

This article deals with the effect of sintering temperature on the physical and chemical characteristics of hydroxyapatite microspheres (HAMs) obtained by spray drying method. A set of specimens were sintered in a conventional furnace at 500–1100°C. The surface morphology, phase composition, size distribution, specific surface area, and porosity were characterized by scanning electron microscope, X-ray diffractometer, laser diffraction particle size analyzer, and specific surface area analyzer, respectively. The results indicated that at 800°C, hydroxyapatite crystals began to grow and were sintered together, which caused a drastic decrease in both the specific surface area and the pore volume. Great changes took place on the surfaces of HAMs during sintering. When the samples were sintered at the temperature of 500 and 600°C, no obvious changes can be found on the surfaces of the samples, but at 800°C, open-micropore surfaces came forth. Besides, the dispersibility of the samples decreased at high temperature (1100°C) because small particles tended to aggregate together. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008