ALKOXIDE ROUTE FOR PREPARING HYDROXYAPATITE AND ITS COATINGS

The preparation of hydroxyapatite using n-butanol or ethanol solutions of P2O5 and Ca glycoxide as precursors of P and Ca was investigated b y nuclear magnetic resonance (NMR), X-Ray Diffraction (XRD) and Scanni ng Electron Microscopy (SEM). Stable mixed solutions of the precursors could be obtained in the presence of acetic acid (HOAC). For the mixe d solution of Ca glycoxide with the ethanol solution of P2O5, a lower HOAC/Ca ratio was needed since the ethanol solution of P2O5 contained a lower concentration of H3PO4, a species that easily forms precipitat es in the presence of the Ca containing species. An amorphous powder w as obtained by heating the stable solution of Ca glycoxide and PO(OH)( x)(OEt)(3-x) with an HOAC/Ca ratio of 4 in a hot plate at similar to 1 50 degrees C. Hydroxyapatite (HAP) was directly formed after calcining the amorphous powder at 500 degrees C. The stable mixed solutions of Ca glycoxide and the alcoholic solutions of P2O5 were used to prepare HAP coatings on alumina substrates using a dip-coating method. The res ulting ceramic coatings have a rough surface and an adhesion strength of about 10 MPa. The morphology of the coatings is dependent on the pr eparation chemistry. (C) 1998 Published by Elsevier Science Ltd. All r ights reserved.