Evaluation of Argon-Gas-Injected Solvothermal Synthesis of Hydroxyapatite Crystals Followed by High-Frequency Induction Heat Sintering

In this study, the two-state solvothermal method (180 degrees C) was used for the synthesis of hydroxyapatite nanoparticles. The former is traditional (2, 4 h), and the latter, with argon gas injection (10 bar). To synthesize the powders, a solvent containing dimethylformamide, anhydrous ethanol, diethylene glycol, and water was used. Calcium nitrate tetrahydrate and diammonium hydrogen phosphate were used as calcium and phosphate precursors, respectively. The synthesized powders were consolidated by a high-frequency induction heat sintering method. The powders and sintered samples were then evaluated using X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, and Vickers microindentation technique. The results of this study showed that the powders synthesized in this way are nanometer-sized. The injection of argon gas increased the crystallinity, crystallite size, and particles size. In addition, the injection of argon gas in the powder synthesis phase changed the mechanical properties of the sintered samples. The increase in pressure increased the hardness and elastic modulus. Also, high-frequency induction heat sintering method used in this study achieved high relative density.