NFLUENCE OF BINDER CONCENTRATION ON MORPHOLOGY OFPOROSITY-GRADED HYDROXYAPATITE CERAMICS

This paper describes the slip casting process of Porosity-graded hydroxyapatite ceramics in the presence of Ttiron (1,2-Dihydroxybenzene-3, 5-disulfonic acid disodium salt hydrate) as a dispersant and polyvinyl alcohol as a binder. Zeta potential measurements conducted on hydroxyapatite powder suspensions demonstrated that suspensions with pH > 7 had better stability, and addition of 2wt% PVA did not influenced the isoelectric point remarkably. The suspensions stability and the appropriate amount of tiron were determined by measuring of sedimentation heights. HAP slurries with 10wt% solid loading, 1.9wt% dispersant and different amount of PVA were casted in plaster slabs. Finally, samples were dried in 105cc and subsequently sintered at 900 C. Investigation on morphology and pore size distribution was carried out by SEM. It was found that addition of PVA could improve mechanical strength of green body and porosity volume; however, it could deteriorate porous structure by importing cracks during debinding and sintering phases.

کلیدواژه ها:

porous hydroxyapatite ، slip casting ، binder effect