Behavior of sintered body properties of hydroxyapatite ceramics: effect of uniaxial pressure on green body fabrication

Abstract

Hydroxyapatite (HA) sintered bodies have been made through the pressureless sintering method. Uniaxial compaction pressure was varied from 10 to 190 MPa to obtain the optimum pressure required for manufacturing green bodies. Before the process of making green bodies, HA powder was added with 10 wt% polyvinyl alcohol (PVA) as a binder. The preheating process was carried out at a temperature of 700 °C with a holding time of 1 h to remove PVA, followed by the process of sintering at a temperature of 1200 °C with a holding time of 2 h in the air environment. The properties of HA sintered bodies were studied by characterizing their microstructure and phase and determining their linear shrinkage, density, relative density, and Vickers hardness. The results showed that tangential contact had occurred between the particles at a uniaxial compaction pressure of 40 MPa, as evidenced by good grain bonding found in the sintered bodies. It was found that uniaxial pressures of 130–190 MPa generated grain bonding more perfectly and hardness values that meet the standards for HA sintered bodies. The strengthening mechanism is modeled by illustration as imperfect tangential contact and perfect tangential contact between the powders on the green body.