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5112 |
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Wednesday, May 11, 2016, Room 3G 11:00 AM Modeling & Simulation I |
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Formation mechanism analysis of solution precursor
plasma sprayed hydroxyapatite coatings
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Rolando Jr Candidato* / University of Limoges, France Lech Pawlowski / SPCTS, University of Limoges, France Catalin Constantinescu/ SPCTS, University of Limoges, France Bernard Pateyron/ SPCTS, University of Limoges, France Alain Denoirjean/ SPCTS, University of Limoges, France |
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Hydroxyapatite (HA) is technologically attractive oxide useful for bone implants due to its compositional similarity to the mineral component of human bone. Currently, plasma spraying is the standard method in producing hydroxyapatite coatings for biomedical purposes and is conventionally accomplished using coarse powders. The solution precursor plasma spraying is an emerging coating technique which may be useful for HA deposition. This technique uses liquid precursors which precipitate in plasma jet forming solid HA. The present study uses aqueous solution of: (i) diammonium hydrogen phosphate and calcium hydroxide; and, (ii) calcium nitrate and triethyl phosphite to form HA oxide by plasma spraying. The phenomena occurring after injection of liquid precursor of hydroxyapatite powder were simulated numerically. The simulation started with the calculation of the map of velocity and temperature of working plasma gases. The map was calculated by taking into account the evaporation of the liquids included in the solution. The content of the chemical species included in plasma jet was also calculated. The phenomena of solid precipitation, evaporation, formation of solid shells as well as their spheroidization and agglomeration in large particles were described analytically. Furthermore, microstructural features observed in single scan experiment as well as in the final coating was used for establishing plausible formation mechanism of the deposits in various stages of the in-flight droplets. Finally, optimal spray parameters are set for the deposition of crystalline HA coatings. |