Well-dispersed sol with crystalline hydroxyapatite (HAp) was obtained directly by milling a mixture comprising Ca(OH)_2, an aqueous solution of H_3PO_4 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 mPa s. From the diluted sol, we obtained a few μm thick dense film of HAp by dip coating on the slide glass precoated by chitosan.
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