Nanocrystalline Powders of Alkaline-Earth Phosphates as Precursors for Bioceramics

Bone is a nanocomposite made of calcium phosphates and collagen. Collagen has a typical fibrous structure, with diameter ranging from 100 nm to 2 μm. It is suggested that calcium hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂ in the size range 5-50 nm embedded in the collagen framework provides mechanical strength to bone. Among calcium phosphates, apatites are found to be the most suitable for bone regeneration due to its biocompatibility. A contemporary theme is to prepare nanocrystallites of alkaline-earth phosphates that can be employed as precursors for making novel bioceramics. In this paper, we present our attempts to prepare nano-sized particles of alkaline-earth hydroxyapatites, A₁₀(PO₄)₆(OH)₂ where A= Ca, Sr and Ba through a metathetical route. Our work involved the use of same reactants treated under different reaction conditions. While hydrothermal route yielded well-crystalline nanorods, microwave resulted in agglomerated hydroxyapatites and reverse micellear route gave low crystalline apatites with less agglomeration.