Hydroxyapatite formation by solvothermal treatment of α-tricalcium phosphate with water–ethanol solution

We investigated hydroxyapatite (HAp) formation from alpha-tricalcium phosphate (α-TCP) under solvothermal conditions using water–ethanol solution. The rate of HAp formation decreased with increasing ethanol fraction in the solution. Needle-like HAp was formed with a small amount of beta-tricalcium phosphate after solvothermal treatment for 3 h in solutions with water/ethanol volume ratios of 5/15 and 10/10. In the solution with water/ethanol volume ratio of 5/15, needle-like HAp formed with a small amount of dicalcium phosphate anhydrous (DCPA) at 12 h, and the amount of DCPA increased with increasing treatment period. The aspect ratio of the HAp crystals that formed increased with increasing ethanol fraction in the solution. The fraction of ethanol in the solution during the solvothermal processing affects not only the rate of transformation of α-TCP into HAp, but also the morphology of the HAp that is formed.