The production and characterization of hydroxyapatite (HA) powders

The synthesis of appropriate calcium phosphate powders for thermal spraying applications is a fundamental yet crucial stage in the production of a bio ceramic 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 coa tings from thermal spray processes, spherical powders of a specified size d istribution are recommended. Such spherical morphology has been proven to p roduce excellent heat transfer characteristics and consistent melting behav iour, which would increase the deposition efficiency and decrease coating p orosity. This paper aims to provide an insight to the preparation and chara cterization aspect of HA powders by the spray drying process. The raw HA po wders were synthesized through a chemical reaction involving orthophosphori c acid and calcium hydroxide. The precipitated spray dried powders were exa mined for purity, phase composition and morphology. The heat-treated powder s were then flame spheroidized to produce spherical, high flowability powde rs to be used as feed-stock for plasma spraying. (C) 1999 Published by Else vier Science S.A. All rights reserved.