ATOMIC-FORCE MICROSCOPY OF ANODIZED ZIRCONIUM SUBSTRATES

Atomic force microscopy (AFM) has been employed to probe the detailed surface morphology of chemically polished and electropolished zirconiu m substrates. Whilst the results are qualitatively similar to those fr om transmission electron microscopy of carbon replicas of the treated surfaces, AFM allows ready quantification of the surface morphology in three dimensions. Furthermore changes in surface morphology, associat ed with growth of relatively thin anodic oxide films on the respective surfaces, have been revealed by AFM. The developments of a subtle rou ghness was displayed after anodizing chemically polished zirconium. wh ilst anodizing an originally electropolished surface revealed no chang es in surface morphology. Such behaviour is related to the film growth mechanism on the respective substrates. Non-uniform film growth on th e chemically polished zirconium arises through the presence of preferr ed paths for ionic conduction within the fluoride-contaminated, amorph ous anodic film developed initially on the chemically polished substra te and leads to an amorphous to crystalline transition. For the electr opolished surface, crystalline anodic zirconia develops from the comme ncement of anodization of the highly flat substrate.