Hydraulicity of the Dicalcium Phosphate-Calcium Carbonate Mixture and Properties of the Resulting Porous Apatite

Abstract

Dihydrate (CaHPO₄⋅2H₂O; DCPD) and anhydride (CaHPO₄; DCPA) of dicalcium phosphate are studied on their hydraulicity (hydration and hardening) induced by the addition of CaCO₃ and properties of the resulting porous apatite. The hardening was caused by the entanglement of microcrystals of reaction products, i.e., carbonate-containing apatite and/or octacalcium phosphate. DCPD is hydrated and hardens more easily than DCPA. The addition of F^- accelerates the hydration reaction remarkably, however no hardening occurs. The resulting hardened apatite bodies have 70-80% porosity and a diametral tensile strength of 0.3-1.5MPa. Sintered apatite bodies prepared by heating the hardened bodies are densified to 45-60% and strengthened to 0.7-4.8MPa. An apatite packed column for HPLC (high-performance liquid chromatography) prepared by using the hydraulicity has a high flow rate (1.39ml/min·cm² at pressures of 1-2kgf/cm²), but it shows a low resolution producing chromatographic peaks with a large width; this is probably due to a heterogeneous packing structure.