A comparative study of hydroxyapatites synthesized using various fuels through aqueous and alcohol mediated combustion routes

Nano-sized calcium hydroxyapatite, [Ca10(PO4)6(OH)2] has been synthesized by the sol–gel combustion method using calcium nitrate and di-ammonium hydrogen phosphate as precursors in the aqueous medium. Triethyl phosphite was used as a phosphate precursor for alcohol mediated combustion. The aqueous and alcohol media were employed for the investigation of combustion synthesis in the presence of various fuels such as urea, glycine, alanine, hydrazine and hexamine. The metal-to-fuel ratio in the synthesis was maintained at 1 to facilitate complete combustion and the Ca/P ratio was maintained at 1.67 to aid the stoichiometric formation of hydroxyapatite. The combustion products were calcined at 800 °C for 10 h and were characterized by powder XRD, FT-IR, HR-SEM and HR-TEM techniques. All the five fuels used under the alcohol mediated combustion, resulted in forming phase pure hydroxyapatite; whereas the aqueous mediated combustion method yielded biphasic calcium phosphate containing Ca10(PO4)6(OH)2 and β-TCP depending on the nature of the fuel.

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