Study on hydroxyapatite nanopowder prepared by low-temperature combustion synthesis

Using Ca(NO₃)₂·4H₂O,(NH ₄)₂HPO₄ and citric acid as crude materials, concentrated nitric acid as solvent and NH₄NO₃ as combustion promoter, based on its chemical composition and the theory of combustion, hydroxyapatite nanopowder was prepared by low-temperature combustion synthesis (LCS) and hydrothermal technique. The phase composition and morphology of the combustion products and the powder by hydrothermal synthesis were investigated by XRD and SEM (cold field emission). Results show that the best molar ratio of Ca(NO₃)₂·4H₂O, (NH₄)₂HPO₄ and citric acid is 5:3:2.2, and the composition of the main crystal phase of the precursor powder prepared by LCS is nanosized HAP. Its grain sizes are between 40 nm to 80 nm after treated by hydrothermal synthesis. After 2 h hydrothermal treatment, the crystallinity of HAP is raised, its main shape of particles is columnar, the columnar sizes are in the range of 50 nm∼80 nm in diameter and 100 nm∼130 nm in length.