Tantalum (Ta) is a metal with excellent corrosion resistive properties and recen

Question

Tantalum (Ta) is a metal with excellent corrosion resistive properties and recently shown to have good biocompatibility. A few groups have begun to evaluate the potential use in biomedical applications. However, one major limitation is complicated fabrication techniques and high expense associated with Ta. Therefore, researchers are looking to surface modification techniques to employ a stable, inexpensive base metal that can then be coated with Ta. One such combination is Ta coated titanium alloys used for orthopedic applications. a. Yu etal 2015 recently explored chemical vapor deposition as a mechanism to coat titanium alloy (Ti6Al4V). Describe this surface modification technique. b. Name and describe one surface analysis technique the researchers could use to verify presence or absence of the Ta surface coating. Include What control and experimental samples to include. c. The researchers would also like to evaluate potential alterations surface topographical alterations after Ta-coating. Name and describe one topographical analysis technique the researchers could use here. Include control and sample groups.

Explanation / Answer

Determining the bulk composition of the tantalum coating is a paradox, as ppm-level impurities are relevant, a common surface analysis method like SEM/EDX, AES or XPS, is not sensitive enough in this concentration level. Further, the tantalum layer is relatively thin and traditional wet analysis is not feasible. TOF-SIMS (Time-of-flight secondary ion mass spectroscopy using Ga+ generated by a Ga gun (working voltage 25 kV) as primary ions is used as a method for analysing the Tantalum layer. Using this method, it is possible to detect and quantify ppm level impurities in the relatively thin surface coating without interference from the substrate material or the native oxide layer, always present on tantalum surfaces, exposed to the atmosphere.

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