Abstract
Calcium phosphate (Ca-P) coatings have been used as surface coatings on porous metallic implants in dentistry and orthopaedics for the last twenty years. These Ca-P coatings, nominally hydroxyapatite (HA), have been shown to promote bone fixation and osteconductivity on Ti and Ti alloy substrates used for those purposes. Such coatings can be formed by different methods including plasma spray. In addition to the well known advantages of the plasma spray technique to deposit coatings, a new version of this technique, i.e. solution precursor plasma spray (SPPS), has been reported to produce submicron/nanocrystalline structured coatings. Nanocrystalline HA coatings may improve the resorption of the coating in the body, avoiding the irritant effect of large particles which may be seen in current thermal sprayed HA coatings. The main purpose of this work was to study the suitability of a sol-gel Ca-P solution precursor (calcium nitrate tetrahydrate and ammonium dihydrogen phosphate) as feedstock for the air plasma spray (APS) coating technique. We report on the formation and the characteristics of the coatings so formed on Ti6Al4V substrates. The presence of different Ca-P crystalline and amorphous phases was assessed by X-ray diffraction analysis. The X-ray photoelectron spectroscopy technique was used to characterize the surface chemical composition of the Ca-P coatings. The microstructural features of the coatings were characterized by scanning/transmission electron microscopy combined with image analysis in order to evidence the presence of submicron/nanocrystalline Ca-P features. Final results are discussed in terms of the spraying parameters. Abstract only; no full-text paper available.
