Powder Mixture for the Production of Microporous Ceramics Based on Hydroxyapatite

Abstract

Powder mixtures with a given molar ratio of Ca/P = 1.67 were prepared under mechanical activation conditions from hydroxyapatite powder Ca10(PO4)6(OH)2 and a 1M aqueous solution of oxalic acid H2C2O4 at a molar ratio of Ca10(PO4)6(OH)2/H2C2O4 = 1:4. The phase composition of obtained powder mixture included brushite (calcium hydrophosphate dihydrate) CaHPO4·2H2O, calcium oxalate monohydrate CaC2O4·H2O in form of whewellite and weddellite, and some quantity of quasi-amorphous phase. This powder mixture was used to produce microporous monophase ceramics based on hydroxyapatite Ca10(PO4)6(OH)2 with apparent density of 1.25 g/cm3 after firing at 1200 °C. Microporosity of sintered ceramics was formed due to the presence of particles with plate-like morphology, restraining shrinkage during sintering. Microporous ceramics based on hydroxyapatite Ca10(PO4)6(OH)2 with the roughness of the surface as a consequence of the created microporosity can be recommended as a biocompatible material for bone defects treatment and as a substrate for bone cell cultivation.

Microporous Ceramics Based on β-Tricalcium Phosphate

“…Various methods can be used to achieve microporosity of ceramic materials. Among them are incomplete sintering [39], addition of small particles of sacrificial organic or inorganic components to the starting powder mixture [40,41], addition of components having the ability to release of sufficiently large volumes of gases when heated [42], using the sol-gel method of precursor preparation [43], or using a powder mixture containing columnar-like [44] or plate-like [45] particles restraining densification. Synthesized powders of dicalcium phosphate dihydrate CaHPO 4 •2H 2 O and/or dicalcium phosphate anhydrate CaHPO 4 (i.e., brushite and/or monetite) usually consist of plate-like or petal-like particles [46][47][48][49].…”