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

Abstract

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 degrees 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 degrees 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 degrees C, no obvious changes can be found on the surfaces of the samples, but at 800 degrees C, open-micropore surfaces came forth. Besides, the dispersibility of the samples decreased at high temperature (1100 degrees C) because small particles tended to aggregate together.

Synthesis and characterization of strontium-doped hydroxyapatite for biomedical applications

“…It is known that owing to the low process temperature, spray-dried powders have significant amount of absorbed water [40,41]. In this case, spray-dried pure and Sr-doped HA powders could be lost mass on a large scale up to 150°C.…”

Sustained Efficacy of Erythropoietin with a Hydroxyapatite Carrier Administered in Mice

“…Nagao et al has reported that HAp has the ability to absorb therapeutic agents without deactivation and shows regulated release as it biodegrades [22]. The biodegradation speed of HAp can be regulated by calcination temperature [19,23,31]. Spray-drying has been shown to be a good fabrication method for spherical porous HAp powder with a high specific surface area of more than 60 cm 3 /g [23,31].…”

“…The biodegradation speed of HAp can be regulated by calcination temperature [19,23,31]. Spray-drying has been shown to be a good fabrication method for spherical porous HAp powder with a high specific surface area of more than 60 cm 3 /g [23,31]. Mizushima et al [19] recently reported the possibility of the sustained release of proteins and lipophilic drugs using injectable HAp microparticles.…”

In situ fabrication of hollow hydroxyapatite microspheres by phosphate solution immersion

“…It is shown that the pore size distribution of the hollow HAP microspheres was mainly the mesopores in the range of 2-40 nm, and the mean pore size was 10.5 nm. In general, the widely accepted definitions of the pore size ranges are: micropores o2 nm, mespores 2-50 nm, and macropores 450 nm [21]. The BET and BJH test results showed that the specific surface areas and the total pore volume of hollow HAP microspheres are 120.43 m 2 /g and 0.5614 cm 3 /g, respectively.…”