Molten Salt Synthesis of Calcium Hydroxyapatite Whiskers

Calcium hydroxyapatite (HA) whiskers and crystals were produced by the route of molten salt synthesis. The effects on whisker morphology of chosen flux, flux-to-HA ratio, synthesis temperature, and reaction time were investigated. The thermal stabilities of the produced whiskers were tested at 1300°C in an air atmosphere. A tentative X-ray diffraction pattern was proposed for the HA whiskers. Molten salt synthesis with a K₂SO₄ flux was found to be a simple and sturdy technique for manufacturing short (≤60 μm) HA whiskers in the temperature range from 1080° to ∼1200°C. The alternative use of fluxes such as KCl, KBr, CaCl₂, or Na₂SO₄, rather than K₂SO₄, over the temperature range 850°–1000°C resulted in the formation of large (∼25 μm) single crystals of HA.