Study on Hollow Hydroxyapaptite Microspheres Prepared by a Borate Glass Conversion Process

Hollow hydroxappatite (HAP) microspheres consisting of a hollow core and a porous shell were prepared by a Li-Ca-B glass conversion process. The phase composition, morphology and pore structure on the shell wall were investigated using XRD, SEM and BET. The results showed that the asprepared microspheres possessed good internal hollow structure. The shell wall of the microsphere was made up of HAP crystals fully. After heattreated at 600℃ for 2h, the compressive strength of the microsphere was determined to be (2.1±0.6)MPa, and the porosity and pore size of the shell wall were 85% and 60nm, respectively. Furthermore, the formation mechanism of the hollow HAP microsphere was also suggested. In phosphate solution, Ca-P-OH hydrate was in-situ formed on the surface of the glass and precipitated in the position initially occupied by Ca2+, while the pores were formed in the position initially occupied by Li+ and B3+. These hollow HAP microspheres may be useful for drug delivery.