Gas injection approach for synthesis of hydroxyapatite nanorods via hydrothermal method

Hydroxyapatite nanorods were synthesized with a new strategy by mixing hydrogen (15%) and argon (85%) gas injected into hydrothermal autoclave. Calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions were used as precursors. These materials were mixed together to maintain Ca/P ratio of 1.67. The final solution pH was adjusted with ammonia solution and transferred to the autoclave for hydrothermal process. The temperature and pH were set to 180 o C and 11 respectively. Powder synthesis was carried out once without gas injection, which was 10 h. The powders synthesized at 5, 10, and 15 h by injecting the gas mixture. The synthesized powders were characterized with Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, X-ray diffraction, High-resolution transmission electron microscopy, and Raman spectroscopy. The results showed that use of injected gas increased crystallinity and crystallite size. Also, the use of gas injection has increased the hardness and elastic modulus.