The production and characterization of hydroxyapatite (HA) powders

Abstract

The synthesis of appropriate calcium phosphate powders for thermal spraying applications is a fundamental yet crucial stage in the production of a bioceramic coating coupled with the desired characteristics. The performance, lifespan and quality of the resultant biological coating in vivo is largely dependent on the coating morphology, phase composition, particle size and crystallinity of the spray powders. In order to achieve highly reliable coatings from thermal spray processes, spherical powders of a specified size distribution are recommended. Such spherical morphology has been proven to produce excellent heat transfer characteristics and consistent melting behaviour, which would increase the deposition efficiency and decrease coating porosity. This paper aims to provide an insight to the preparation and characterization aspect of HA powders by the spray drying process. The raw HA powders were synthesized through a chemical reaction involving orthophosphoric acid and calcium hydroxide. The precipitated spray dried powders were examined for purity, phase composition and morphology. The heat-treated powders were then flame spheroidized to produce spherical, high flowability powders to be used as feed-stock for plasma spraying.