Hydroxyapatite nano sol prepared via a mechanochemical route

Well-dispersed sol with crystalline hydroxyapatite (HAp) was obtained directly by milling a mixture comprising Ca(OH)₂, an aqueous solution of H₃PO₄ and a dispersant, an ammonium salt of polyacrylic acid. The average crystallite size of HAp was below 20 nm. Ca/P molar ratio of the product was 1.51 ± 0.04, i.e. Ca deficient from stoichiometric HAp. Minimum apparent viscosity was attained at a dispersant concentration 0.92wt% of sol. An as-milled sol was diluted by a factor 10-2.61 solid wt% to give a Newtonian fluid of 2 mPas. From the diluted sol, we obtained a few μm thick dense film of HAp by dip coating on the slide glass precoated by chitosan.