The alkoxide sol-gel process in the calcium phosphate system and its applications

A single calcium glycolate was synthesized. The alkoxide was stable under a mbient atmosphere. The calcium glycolate, phosphoric acid and P(OH)(x)(OEt) (3-x) were used as the precursors. Acetic acid was used as a reagent to mod ify the calcium glycolate and to change the acidity of the mixtures of the precursors. Mixtures of the calcium glycolate and phosphoric acid in a Ca/P ratio of 1.67 showed unusual sol-gel behavior. A transparent gel could be formed depending on the content of acetic acid and the extent of stirring. The behavior is attributed to el high viscosity and a large molecular size of the ethylene glycol solvent, leading to a strong dependence of the react ions in the mixtures on the diffusion process, greatly affected by stirring . When the mixtures of the calcium glycolate and PO(OH)(x)(OEt)(3-x) contai ned acetic acid at an acetic acid/Ca ratio of 3, stable alkoxide solutions with Ca/P ratios of 1.0, 1.5 and 1.67 could be formed. Different calcium ph osphate compounds and hydroxyapatite coatings on alumina substrates could e asily be formed from the alkoxide solutions, The chemical homogeneity provi ded by the alkoxide route leads to easy formation of the required products. Copyright (C) 1999 John Wiley & Sons, Ltd.