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Rod-like hydroxyapatite nanoparticles (n-HAp) with a highly ordered nanostructure were prepared by hydrothermal synthesis from calcium chloride, and phosphoric acid, as calcium and phosphorus sources, respectively. Various surfactant families such as cationic (CTAB), anionic (SDS) and nonionic (Triton X-100) were used as regulators of the nucleation and crystal growth. The synthesized nanopowders were characterized using X-ray diffraction (XRD), Fourier transform infrared spectrograph (FTIR) and transmission electron microscopy (TEM). The rod-like morphology was obtained regardless of the surfactant used during the hydrothermal treatment, but the aspect ratio of the crystals was found to be surfactant dependent. The mechanism of crystal growth as well-oriented nanostructure is discussed.

Si‐doped hydroxyapatite nanoparticles (n‐SixHA) were prepared by hydrothermal synthesis from calcium nitrate tetrahydrate and diammonium hydrogen orthophosphate. A rod‐like morphology was obtained for all the powders irrespective of the incorporated Si‐doping level. But the crystallinity of the n‐SixHA powders, the density achieved upon sintering powder compacts and their mechanical properties (three‐point‐bending strength), as well as their biomineralization activity evaluated by immersing them into simulated body fluid (SBF) were found to be dependent on the Si‐doping amount.

Surfactant‐assisted hydrothermal synthesis of magnesium‐doped hydroxyapatite (Ca10−xMgx(PO4)6(OH)2) with 0 ≤ x ≤ 1) was realized in aqueous solution at 90°C. β‐TCP phase was formed in the Mg0.6‐HA sample after heat treatment at 1000°C. Magnesium was found to degrade the sintering ability of Mgx‐HA ceramics. Flexural strength (σf) was found to decrease as a function of Mg‐doped HA. The using of carbon nanotubes as reinforcing agents mitigated the strength loss of Mg‐HA ceramics. The flexural strength of Mg0.6‐HA was then increased by nearly 20% from approximately 33 to 39 MPa with an optimum addition of 3 wt% of multi‐walled nanotubes.

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