Synthesis of fluor-hydroxyapatite powder for plasma sprayed biomedical coatings: Characterization and improvement of the powder properties

• The physical properties including the low flowability of the powders were investigated by an ethanol treatment as solvent to significantly improve the flowability.
• The surface tension measurements following the Van Oss method indicates that the powders having a low value of have a tendency not to flow and an ethanol treatment allows increasing this value.
• Powder wettability and flowabilityt are critically important for manufacturing biomedical plasma-sprayed coatings.

Fluor-hydroxyapatite (FHA) powder was synthesized by double decomposition in a view to produce bioactive and thermally stable coatings by plasma spray process. This work aims at studying the influence of chemical composition, microstructure and surface energy on the flowability of the FHA particles which is known as a determinant property during plasma spraying for the quality of the product in terms of yield and homogeneity of composition. The as-synthesized FHA powder was sieved in order to obtain two ranges of particles size: 50–80 μm and 80–100 μm. The phase composition and structure and physical characteristics of FHA particles have been determined by complementary analytical techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron spectroscopy and laser granulometry). Then, the FHA flowability was determined as recommended by the European Pharmacopeia.The results showed that the 80–100 μm FHA powder has a longer flow time compared to a reference hydroxyapatite powder whereas the 50–80 μm FHA particles did not flow. We propose a simple treatment of the FHA particles using ethanol as solvent which showed to significantly improve the flowability of FHA powders.

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