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 as-prepared microspheres possessed good internal hollow structure. The shell wall of the microsphere was made up of HAP crystals fully. After heat-treated at 600°C 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 60 nm, 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.