HIGHLY ADHESIVE HYDROXYAPATITE COATINGS ON ALUMINA SUBSTRATES PREPARED BY ION-BEAM-ASSISTED DEPOSITION

Ion-beam assisted deposition (IBAD) was carried out to deposit hydroxy apatite (HAp) on alumina substrate. The amorphous coating layer on alu mina substrate is crystallized to the dense HAp after a post-treatment process of annealing at 500 degrees C for 2 h and immersion in deioni zed water for 72 h at room temperature. The homogeneous and dense HAp coating is observed by scanning electron microscopy and the thickness of the coating is measured to be about 638 nm. The hardness of the coa ting layer in the as-deposited and post-treated samples is 475 and 508 , respectively. The adhesive strength between HAp and a-alumina substr ate was measured by a scratch lest. The ion-beam sputtered coatings we re used as control samples. The adhesion was found to be worse for ion -beam sputtering deposition (IBSD) than for IBAD. (C) 1998 Elsevier Sc ience S.A.