SOL-GEL SILICA-BASED Ag-Ca-P COATINGS WITH AGGRESSIVE PRETREATMENT OF TITANIUM SUBSTRATE

Thin silica coatings were deposited on titanium by the sol-gel method, using mechanical and chemical pretreatments of the titanium substrates. The solutions were based on TEOS. For the sol-gel dipping process, four different solutions were prepared: silica, silica with AgNO3 and silica + AgNO3 with brushite (CaHPO4.2H2O) or monetite (CaHPO4) powders. The solutions were aged for 7 and 14 days at laboratory temperature. After deposition, the samples were dried and fired. The adhesion of the fired coatings and their bioactivity were tested. The surfaces of the samples were observed after firing, tape testing and in-vitro testing. The firing results showed that silica-silver coatings did not change, brushite sol-gel coatings had cracks and the monetite sol-gel coatings were also cracked, but less so than the brushite coatings. The cracking did not affect the adhesion of the coatings. The results of in-vitro tests showed that all the coatings interacted with simulated body fluid (SBF). After immersion in SBF, a new layer formed on the substrates. For 7-day aged coatings containing brushite, the new layer was uniform and compact and, for coatings containing monetite, the new layer was formed by crystal aggregation. The monetite and brushite coatings prepared from 14-day aged sol were thicker and in-vitro tests confirmed the presence of dellaite, titanate and hydroxyapatite phases.