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Microstructural evolution in laser surface alloying of titanium with iridium

Scripta Materiala, Vol 37, No 5, pp 561-568, 1997

I Manna, W M Steen, K G Watkins

Neural stimulation electrodes have wide ranging applications as human prosthesis, e.g. to simulate auditory function (in cochlear implants), alleviate pain (in tinitus), activate paralyzed limbs (in neuro-muscular disorders), stimulate cardiovascular organs (in pacemaker), treat spinal injury or epilepsy, etc. At present, Ir is amongst the most popular materials used as neural stimulation electrode as the activated multilayered IrO film is known to possess one of the highest charge carrier or current density. However, Ir is expensive, brittle (not suitable for wire-drawing), and being a noble metal, least amenable to etching or lithography. On the other hand, Ti is relatively cheap, ductile and bio-compatible. Therefore, formation of an Ir-rich alloyed zone on top of a thin Ti wire may offer a cheaper and more appropriate substitute for pure-Ir electrodes. In this study laser surface alloying (LSA) of Ir on to thin Ti wires to develop an Ir-rich alloy zone has been adopted and microstructural evolution in the course of LSA traced.

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