engleski

Analysis of coatings on the surface of nitinol formed by ALD process

Nitinol is nearly equiatomic shape memory alloy of nickel and titanium, which is as a result of its good mechanical properties, high corrosion resistance and biocompatibility primarily used in medicine as stents, for flexible parts of surgical instruments, and due to superelastic properties also in dentistry. Nitinol is, because of the application in the human body, in contact with aggressive medium which increases the possibility of the occurrence of corrosion. A consequence of corrosion activity is also nickel releasing that can induce toxic, allergic and hypersensitive reactions in the human body. Therefore, a nitinol surface should be passivated with a coating of appropriate thickness. On nitinol surface TiN and TiO2 layers were deposited using Atomic Layer Deposition (ALD) technique. ALD is a thin film deposition method in which a film is grown on a substrate by exposing its surface to alternate gaseous species (precursors). The precursors are inserted in reactor as a series of sequential pulses. In each of these pulses the precursor molecules react with the surface so that the reaction terminates once all the reactive sites on the surface are consumed. By varying the number of cycles it is possible to grow layers uniformly and with high precision on arbitrarily complex and large substrates. Such obtained samples were analyzed for biocompatibility and corrosion resistance in comparison to nitinol without coating.

Nitinol, ALD

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