Evaluating sol-gel ceramic thin films for metal implant applications: III.In vitro aging of sol-gel-derived zirconia films on Ti-6Al-4V

Sol-gel-derived zirconia films were deposited onto polished Ti-6Al-4V subst rates by dip-coating from an alkoxide precursor solution. No change in morp hology of the zirconia him was observed after aging at 37 degrees C for 4-1 2 weeks in pH 4.0 buffer solution or Hanks' balanced salt solution (HBSS), although a precipitate predominantly composed of? calcium phosphate,vas for med on those films aged in HBSS. X-ray diffraction identified the phase of the zirconia him as either cubic or tetragonal, and revealed no degradation to the monoclinic phase after aging, By a substrate straining test, the fr acture strain of the coating was revealed to be 1.5%, above the yield strai n of the titanium alloy substrate. At this strain level, through-thickness cracks formed in the coating where slip bands emerged from the substrate. Q ualitatively, the adhesion of the film was sufficient to prevent gross dela mination of the film at high strain levels, although small regions of delam ination were caused by compressive buckling of the film. This behavior indi cates generally good adhesion. No change in this behavior was observed afte r aging. (C) 1999 John Wiley & Sons, Inc.