Fabrication of Calcium Phosphate Coatings by the Inflight Reaction of Precursor Feedstocks Using Plasma Spraying

Abstract

AbstractHydroxyapatite (Ca10(PO4)6(OH)2) coatings are often made in a two-step process, where hydroxyapatite is firstly synthesized, and then applied as a coating for different applications. One way to make the process more efficient, is to combine the synthesis and coating processes into a single step. Plasma spray is a common method used to apply hydroxyapatite as a coating, as it is a fast and controlled method of coating materials. The aim of the present study was to investigate the inflight reaction of calcium carbonate (CaCO3) and brushite (CaHPO4·2H2O) to synthesize hydroxyapatite using plasma spray. Various plasma spray parameters were used to observe their effect on the quantity of hydroxyapatite produced in the coating. Phase analysis was carried out using XRD, and the morphology of the coatings was observed using SEM. Plasma spray coatings containing hydroxyapatite, tetracalcium phosphate (Ca4(PO4)2O) and calcium oxide (CaO) were successfully made from the reaction between the precursor powders. The plasma spray parameters which influenced the particle velocity were found to have the largest effect on the quantity of hydroxyapatite produced in the coating. The plasma temperature was also found to affect the amount of hydroxyapatite produced.