Preparation of Nanophase Hydroxyapatite via Self Propagating High Temperature Synthesis

Abstract

Nano hydroxyapatite (nHAP) is known to exhibit enhanced biological response when interacting with cells. Phase pure HAP nanoparticles were synthesized by self-propagating high temperature synthesis (SHS) using citric acid and urea as fuels and aqueous precipitation with calcium nitrate and ammonium hydrogen phosphate. The effects of the critical factors governing the synthesis protocols such as pH, reaction and calcination temperatures on the stoichiometry, crystallinity, crystal size, and shape of the nano HAP powders are reported. The results indicated that the crystal sizes varied with some agglomeration in the nanoregime of 10-80 nm, which is comparable to the size of natural nanocrystalline HAP found in human bones and teeth. The influence of grain size, sintering temperature and density of bodies using nHAP as precursor is discussed. Microstructure, crystal structure, morphology, surface area of nHAP powders and dense bodies were investigated using differential thermal analysis and thermal gravimetry analysis (DTA-TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and particle size analysis.